21701920657 has 2 divisors, whose sum is σ = 21701920658. Its totient is φ = 21701920656.

The previous prime is 21701920637. The next prime is 21701920693. The reversal of 21701920657 is 75602910712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13539882321 + 8162038336 = 116361^2 + 90344^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21701920657 is a prime.

It is not a weakly prime, because it can be changed into another prime (21701920637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850960328 + 10850960329.

It is an arithmetic number, because the mean of its divisors is an integer number (10850960329).

Almost surely, 2^21701920657 is an apocalyptic number.

It is an amenable number.

21701920657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21701920657 is an equidigital number, since it uses as much as digits as its factorization.

21701920657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 52920, while the sum is 40.

The spelling of 21701920657 in words is "twenty-one billion, seven hundred one million, nine hundred twenty thousand, six hundred fifty-seven".