21661031216604 has 48 divisors (see below), whose sum is σ = 54626782897568. Its totient is φ = 6640871539968.

The previous prime is 21661031216599. The next prime is 21661031216609. The reversal of 21661031216604 is 40661213016612.

It is an interprime number because it is at equal distance from previous prime (21661031216599) and next prime (21661031216609).

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661031216609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 250593547 + ... + 250679970.

Almost surely, 2^{21661031216604} is an apocalyptic number.

It is an amenable number.

21661031216604 is an abundant number, since it is smaller than the sum of its proper divisors (32965751680964).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661031216604 is a wasteful number, since it uses less digits than its factorization.

21661031216604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 501273814 (or 501273812 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 39.

The spelling of 21661031216604 in words is "twenty-one trillion, six hundred sixty-one billion, thirty-one million, two hundred sixteen thousand, six hundred four".