21319731 has 6 divisors (see below), whose sum is σ = 30795180. Its totient is φ = 14213148.

The previous prime is 21319703. The next prime is 21319741. The reversal of 21319731 is 13791312.

It is not a de Polignac number, because 21319731 - 2⁵ = 21319699 is a prime.

It is a super-2 number, since 2×21319731² = 909061859824722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21319695 and 21319704.

It is not an unprimeable number, because it can be changed into a prime (21319741) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1184421 + ... + 1184438.

It is an arithmetic number, because the mean of its divisors is an integer number (5132530).

Almost surely, 2^21319731 is an apocalyptic number.

21319731 is a deficient number, since it is larger than the sum of its proper divisors (9475449).

21319731 is a wasteful number, since it uses less digits than its factorization.

21319731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2368865 (or 2368862 counting only the distinct ones).

The product of its digits is 1134, while the sum is 27.

The square root of 21319731 is about 4617.3294229457. The cubic root of 21319731 is about 277.2855513878.

The spelling of 21319731 in words is "twenty-one million, three hundred nineteen thousand, seven hundred thirty-one".