21913861 has 2 divisors, whose sum is σ = 21913862. Its totient is φ = 21913860.

The previous prime is 21913849. The next prime is 21913933. The reversal of 21913861 is 16831912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19633761 + 2280100 = 4431^2 + 1510^2 .

It is a cyclic number.

It is not a de Polignac number, because 21913861 - 2⁹ = 21913349 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21913831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10956930 + 10956931.

It is an arithmetic number, because the mean of its divisors is an integer number (10956931).

Almost surely, 2^21913861 is an apocalyptic number.

It is an amenable number.

21913861 is a deficient number, since it is larger than the sum of its proper divisors (1).

21913861 is an equidigital number, since it uses as much as digits as its factorization.

21913861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 31.

The square root of 21913861 is about 4681.2243056705. The cubic root of 21913861 is about 279.8377503883.

The spelling of 21913861 in words is "twenty-one million, nine hundred thirteen thousand, eight hundred sixty-one".