21712171656 has 256 divisors, whose sum is σ = 67666752000. Its totient is φ = 5782683648.

The previous prime is 21712171651. The next prime is 21712171661. The reversal of 21712171656 is 65617121712.

It is an interprime number because it is at equal distance from previous prime (21712171651) and next prime (21712171661).

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21712171651) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 15812986 + ... + 15814358.

It is an arithmetic number, because the mean of its divisors is an integer number (264323250).

Almost surely, 2^21712171656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21712171656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33833376000).

21712171656 is an abundant number, since it is smaller than the sum of its proper divisors (45954580344).

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

21712171656 is a wasteful number, since it uses less digits than its factorization.

21712171656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1533 (or 1515 counting only the distinct ones).

The product of its digits is 35280, while the sum is 39.

The spelling of 21712171656 in words is "twenty-one billion, seven hundred twelve million, one hundred seventy-one thousand, six hundred fifty-six".