21631431 has 16 divisors (see below), whose sum is σ = 30240000. Its totient is φ = 13728000.

The previous prime is 21631409. The next prime is 21631439. The reversal of 21631431 is 13413612.

It is not a de Polignac number, because 21631431 - 2¹⁴ = 21615047 is a prime.

It is a super-2 number, since 2×21631431² = 935837614215522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21631398 and 21631407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21631439) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16695 + ... + 17943.

It is an arithmetic number, because the mean of its divisors is an integer number (1890000).

Almost surely, 2^21631431 is an apocalyptic number.

21631431 is a deficient number, since it is larger than the sum of its proper divisors (8608569).

21631431 is a wasteful number, since it uses less digits than its factorization.

21631431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1526.

The product of its digits is 432, while the sum is 21.

The square root of 21631431 is about 4650.9602234377. The cubic root of 21631431 is about 278.6303476765.

The spelling of 21631431 in words is "twenty-one million, six hundred thirty-one thousand, four hundred thirty-one".