21999859957 has 2 divisors, whose sum is σ = 21999859958. Its totient is φ = 21999859956.

The previous prime is 21999859877. The next prime is 21999859961. The reversal of 21999859957 is 75995899912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21939238161 + 60621796 = 148119^2 + 7786^2 .

It is a cyclic number.

It is not a de Polignac number, because 21999859957 - 2²⁷ = 21865642229 is a prime.

It is a super-2 number, since 2×21999859957² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21999859957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21999859967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10999929978 + 10999929979.

It is an arithmetic number, because the mean of its divisors is an integer number (10999929979).

Almost surely, 2^21999859957 is an apocalyptic number.

It is an amenable number.

21999859957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21999859957 is an equidigital number, since it uses as much as digits as its factorization.

21999859957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165337200, while the sum is 73.

The spelling of 21999859957 in words is "twenty-one billion, nine hundred ninety-nine million, eight hundred fifty-nine thousand, nine hundred fifty-seven".