21304631 has 8 divisors (see below), whose sum is σ = 21596160. Its totient is φ = 21015288.

The previous prime is 21304627. The next prime is 21304639. The reversal of 21304631 is 13640312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21304631 - 2² = 21304627 is a prime.

It is a super-2 number, since 2×21304631² = 907774604092322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21304639) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28460 + ... + 29198.

It is an arithmetic number, because the mean of its divisors is an integer number (2699520).

Almost surely, 2^21304631 is an apocalyptic number.

21304631 is a deficient number, since it is larger than the sum of its proper divisors (291529).

21304631 is a wasteful number, since it uses less digits than its factorization.

21304631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1093.

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 21304631 is about 4615.6939889902. The cubic root of 21304631 is about 277.2200721264.

Adding to 21304631 its reverse (13640312), we get a palindrome (34944943).

The spelling of 21304631 in words is "twenty-one million, three hundred four thousand, six hundred thirty-one".