21631501 has 2 divisors, whose sum is σ = 21631502. Its totient is φ = 21631500.

The previous prime is 21631483. The next prime is 21631507. The reversal of 21631501 is 10513612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18498601 + 3132900 = 4301^2 + 1770^2 .

It is a cyclic number.

It is not a de Polignac number, because 21631501 - 2⁵ = 21631469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21631507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10815750 + 10815751.

It is an arithmetic number, because the mean of its divisors is an integer number (10815751).

Almost surely, 2^21631501 is an apocalyptic number.

It is an amenable number.

21631501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21631501 is an equidigital number, since it uses as much as digits as its factorization.

21631501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 21631501 is about 4650.9677487594. The cubic root of 21631501 is about 278.6306482284.

The spelling of 21631501 in words is "twenty-one million, six hundred thirty-one thousand, five hundred one".