21901631 has 2 divisors, whose sum is σ = 21901632. Its totient is φ = 21901630.

The previous prime is 21901619. The next prime is 21901637. The reversal of 21901631 is 13610912.

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-21901631 is a prime.

It is a super-2 number, since 2×21901631² = 959362880920322, 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 = 21901597 and 21901606.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21901637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10950815 + 10950816.

It is an arithmetic number, because the mean of its divisors is an integer number (10950816).

Almost surely, 2^21901631 is an apocalyptic number.

21901631 is a deficient number, since it is larger than the sum of its proper divisors (1).

21901631 is an equidigital number, since it uses as much as digits as its factorization.

21901631 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 21901631 is about 4679.9178411592. The cubic root of 21901631 is about 279.7856820868.

The spelling of 21901631 in words is "twenty-one million, nine hundred one thousand, six hundred thirty-one".