31917021561 has 6 divisors (see below), whose sum is σ = 46102364490. Its totient is φ = 21278014368.

The previous prime is 31917021551. The next prime is 31917021583. The reversal of 31917021561 is 16512071913.

It is a happy number.

31917021561 is a `hidden beast` number, since 3 + 1 + 9 + 1 + 70 + 21 + 561 = 666.

It can be written as a sum of positive squares in only one way, i.e., 25381269225 + 6535752336 = 159315^2 + 80844^2 .

It is not a de Polignac number, because 31917021561 - 2¹³ = 31917013369 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31917021551) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1773167856 + ... + 1773167873.

It is an arithmetic number, because the mean of its divisors is an integer number (7683727415).

Almost surely, 2^31917021561 is an apocalyptic number.

It is an amenable number.

31917021561 is a deficient number, since it is larger than the sum of its proper divisors (14185342929).

31917021561 is a wasteful number, since it uses less digits than its factorization.

31917021561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3546335735 (or 3546335732 counting only the distinct ones).

The product of its (nonzero) digits is 11340, while the sum is 36.

The spelling of 31917021561 in words is "thirty-one billion, nine hundred seventeen million, twenty-one thousand, five hundred sixty-one".