21957397709 has 16 divisors (see below), whose sum is σ = 24896289600. Its totient is φ = 19197513216.

The previous prime is 21957397687. The next prime is 21957397711. The reversal of 21957397709 is 90779375912.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21957397709 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21957397739) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 2080157 + ... + 2090685.

It is an arithmetic number, because the mean of its divisors is an integer number (1556018100).

Almost surely, 2^21957397709 is an apocalyptic number.

It is an amenable number.

21957397709 is a deficient number, since it is larger than the sum of its proper divisors (2938891891).

21957397709 is a wasteful number, since it uses less digits than its factorization.

21957397709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19004.

The product of its (nonzero) digits is 7501410, while the sum is 59.

The spelling of 21957397709 in words is "twenty-one billion, nine hundred fifty-seven million, three hundred ninety-seven thousand, seven hundred nine".