21168731 has 4 divisors (see below), whose sum is σ = 21180432. Its totient is φ = 21157032.

The previous prime is 21168713. The next prime is 21168767. The reversal of 21168731 is 13786112.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21168731 - 2²² = 16974427 is a prime.

It is a super-2 number, since 2×21168731² = 896230344300722, 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 = 21168694 and 21168703.

It is not an unprimeable number, because it can be changed into a prime (21168701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2495 + ... + 6968.

It is an arithmetic number, because the mean of its divisors is an integer number (5295108).

Almost surely, 2^21168731 is an apocalyptic number.

21168731 is a deficient number, since it is larger than the sum of its proper divisors (11701).

21168731 is an equidigital number, since it uses as much as digits as its factorization.

21168731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11700.

The product of its digits is 2016, while the sum is 29.

The square root of 21168731 is about 4600.9489238634. The cubic root of 21168731 is about 276.6293617545.

The spelling of 21168731 in words is "twenty-one million, one hundred sixty-eight thousand, seven hundred thirty-one".