21958631 has 2 divisors, whose sum is σ = 21958632. Its totient is φ = 21958630.

The previous prime is 21958609. The next prime is 21958637. The reversal of 21958631 is 13685912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21958631 - 2¹⁸ = 21696487 is a prime.

It is a super-2 number, since 2×21958631² = 964362950788322, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21958591 and 21958600.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21958637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10979315 + 10979316.

It is an arithmetic number, because the mean of its divisors is an integer number (10979316).

Almost surely, 2^21958631 is an apocalyptic number.

21958631 is a deficient number, since it is larger than the sum of its proper divisors (1).

21958631 is an equidigital number, since it uses as much as digits as its factorization.

21958631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 35.

The square root of 21958631 is about 4686.0037345269. The cubic root of 21958631 is about 280.0281901889.

Subtracting from 21958631 its sum of digits (35), we obtain a square (21958596 = 4686²).

The spelling of 21958631 in words is "twenty-one million, nine hundred fifty-eight thousand, six hundred thirty-one".