21109957867 has 2 divisors, whose sum is σ = 21109957868. Its totient is φ = 21109957866.

The previous prime is 21109957853. The next prime is 21109957871. The reversal of 21109957867 is 76875990112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21109957867 is a prime.

It is a super-2 number, since 2×21109957867² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21109057867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554978933 + 10554978934.

It is an arithmetic number, because the mean of its divisors is an integer number (10554978934).

Almost surely, 2^21109957867 is an apocalyptic number.

21109957867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21109957867 is an equidigital number, since it uses as much as digits as its factorization.

21109957867 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1905120, while the sum is 55.

The spelling of 21109957867 in words is "twenty-one billion, one hundred nine million, nine hundred fifty-seven thousand, eight hundred sixty-seven".