21313951 has 2 divisors, whose sum is σ = 21313952. Its totient is φ = 21313950.

The previous prime is 21313933. The next prime is 21313979. The reversal of 21313951 is 15931312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21313951 - 2¹¹ = 21311903 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21313931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656975 + 10656976.

It is an arithmetic number, because the mean of its divisors is an integer number (10656976).

Almost surely, 2^21313951 is an apocalyptic number.

21313951 is a deficient number, since it is larger than the sum of its proper divisors (1).

21313951 is an equidigital number, since it uses as much as digits as its factorization.

21313951 is an evil number, because the sum of its binary digits is even.

The product of its digits is 810, while the sum is 25.

The square root of 21313951 is about 4616.7034775909. The cubic root of 21313951 is about 277.2604907942.

The spelling of 21313951 in words is "twenty-one million, three hundred thirteen thousand, nine hundred fifty-one".