21010173656 has 16 divisors (see below), whose sum is σ = 41711374440. Its totient is φ = 9887140480.

The previous prime is 21010173649. The next prime is 21010173671. The reversal of 21010173656 is 65637101012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77243150 + ... + 77243421.

Almost surely, 2^21010173656 is an apocalyptic number.

It is an amenable number.

21010173656 is a deficient number, since it is larger than the sum of its proper divisors (20701200784).

21010173656 is a wasteful number, since it uses less digits than its factorization.

21010173656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154486594 (or 154486590 counting only the distinct ones).

The product of its (nonzero) digits is 7560, while the sum is 32.

Adding to 21010173656 its reverse (65637101012), we get a palindrome (86647274668).

The spelling of 21010173656 in words is "twenty-one billion, ten million, one hundred seventy-three thousand, six hundred fifty-six".