21709017656 has 8 divisors (see below), whose sum is σ = 40704408120. Its totient is φ = 10854508824.

The previous prime is 21709017611. The next prime is 21709017667. The reversal of 21709017656 is 65671090712.

It is a tau number, because it is divible by the number of its divisors (8).

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 as a sum of consecutive naturals, namely, 1356813596 + ... + 1356813611.

It is an arithmetic number, because the mean of its divisors is an integer number (5088051015).

Almost surely, 2^21709017656 is an apocalyptic number.

It is an amenable number.

21709017656 is a deficient number, since it is larger than the sum of its proper divisors (18995390464).

21709017656 is a wasteful number, since it uses less digits than its factorization.

21709017656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2713627213 (or 2713627209 counting only the distinct ones).

The product of its (nonzero) digits is 158760, while the sum is 44.

The spelling of 21709017656 in words is "twenty-one billion, seven hundred nine million, seventeen thousand, six hundred fifty-six".