21000161656 has 16 divisors (see below), whose sum is σ = 39460722840. Its totient is φ = 10477302240.

The previous prime is 21000161647. The next prime is 21000161671. The reversal of 21000161656 is 65616100012.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2843406 + ... + 2850781.

Almost surely, 2^21000161656 is an apocalyptic number.

It is an amenable number.

21000161656 is a deficient number, since it is larger than the sum of its proper divisors (18460561184).

21000161656 is a wasteful number, since it uses less digits than its factorization.

21000161656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5694654 (or 5694650 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 28.

Adding to 21000161656 its reverse (65616100012), we get a palindrome (86616261668).

The spelling of 21000161656 in words is "twenty-one billion, one hundred sixty-one thousand, six hundred fifty-six".