21715731 has 12 divisors (see below), whose sum is σ = 32097208. Its totient is φ = 14140224.

The previous prime is 21715723. The next prime is 21715741. The reversal of 21715731 is 13751712.

It is a happy number.

21715731 is a `hidden beast` number, since 21 + 71 + 573 + 1 = 666.

It is not a de Polignac number, because 21715731 - 2³ = 21715723 is a prime.

It is a super-2 number, since 2×21715731² = 943145945728722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21715695 and 21715704.

It is not an unprimeable number, because it can be changed into a prime (21715711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27670 + ... + 28443.

Almost surely, 2^21715731 is an apocalyptic number.

21715731 is a deficient number, since it is larger than the sum of its proper divisors (10381477).

21715731 is a wasteful number, since it uses less digits than its factorization.

21715731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56162 (or 56159 counting only the distinct ones).

The product of its digits is 1470, while the sum is 27.

The square root of 21715731 is about 4660.0140557728. The cubic root of 21715731 is about 278.9918292593.

The spelling of 21715731 in words is "twenty-one million, seven hundred fifteen thousand, seven hundred thirty-one".