You say DER, but you tag PGP which doesn't use DER -- and whose publickey block includes a lot of things beyond the RSA values (n,e). The DER encoding of a PKCS#1 RSA publickey of 4096 bits with a conventional e of 65537 (default at least for openssl and Java) is
30 82 02 0a 02 82 02 01 (n with leading 00) 02 03 01 00 01
with a total length of 526 octets. The DER encoding of a generic
SubjectPublicKeyInfo which is always used in X.509 certificates and often in other places (including openssl and Java) adds an outer
AlgorithmIdentifier and a wrapping
BIT STRING giving a total length of 550 octets. If you mean something else, specify it more clearly.
For the private exponent see RSA: Most significant key bit always 1? .
But if you are concerned about the encoding of a private key, that is much more than just the exponent and (possibly) modulus; see https://stackoverflow.com/questions/5403808/private-key-length-bytes . In addition the privatekey is often encrypted, which usually expands the encrypted value and adds metadata about the encryption.
If you have a question about a particular key encoding with a particular program or protocol/format, you need be much more specific.