21431304 has 40 divisors (see below), whose sum is σ = 60029310. Its totient is φ = 7143552.

The previous prime is 21431303. The next prime is 21431309. The reversal of 21431304 is 40313412.

It can be written as a sum of positive squares in only one way, i.e., 18507204 + 2924100 = 4302^2 + 1710^2 .

It is a super-2 number, since 2×21431304² = 918601582280832, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21431303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 15889 + ... + 17184.

Almost surely, 2^21431304 is an apocalyptic number.

21431304 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21431304 is an abundant number, since it is smaller than the sum of its proper divisors (38598006).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21431304 is a wasteful number, since it uses less digits than its factorization.

21431304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33091 (or 33078 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21431304 is about 4629.3956409017. The cubic root of 21431304 is about 277.7684181498.

Adding to 21431304 its reverse (40313412), we get a palindrome (61744716).

The spelling of 21431304 in words is "twenty-one million, four hundred thirty-one thousand, three hundred four".