21431320 has 16 divisors (see below), whose sum is σ = 48220560. Its totient is φ = 8572512.

The previous prime is 21431317. The next prime is 21431341. The reversal of 21431320 is 2313412.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21431294 and 21431303.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 267852 + ... + 267931.

It is an arithmetic number, because the mean of its divisors is an integer number (3013785).

Almost surely, 2^21431320 is an apocalyptic number.

21431320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21431320 is an abundant number, since it is smaller than the sum of its proper divisors (26789240).

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

21431320 is a wasteful number, since it uses less digits than its factorization.

21431320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 535794 (or 535790 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21431320 is about 4629.3973689888. The cubic root of 21431320 is about 277.7684872745.

Adding to 21431320 its reverse (2313412), we get a palindrome (23744732).

The spelling of 21431320 in words is "twenty-one million, four hundred thirty-one thousand, three hundred twenty".