21907913 has 2 divisors, whose sum is σ = 21907914. Its totient is φ = 21907912.

The previous prime is 21907909. The next prime is 21907927. The reversal of 21907913 is 31970912.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21557449 + 350464 = 4643^2 + 592^2 .

It is a cyclic number.

It is not a de Polignac number, because 21907913 - 2² = 21907909 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21907913.

It is not a weakly prime, because it can be changed into another prime (21907943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953956 + 10953957.

It is an arithmetic number, because the mean of its divisors is an integer number (10953957).

Almost surely, 2^21907913 is an apocalyptic number.

It is an amenable number.

21907913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21907913 is an equidigital number, since it uses as much as digits as its factorization.

21907913 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 21907913 is about 4680.5889586675. The cubic root of 21907913 is about 279.8124296479.

The spelling of 21907913 in words is "twenty-one million, nine hundred seven thousand, nine hundred thirteen".