21370831 has 4 divisors (see below), whose sum is σ = 21381192. Its totient is φ = 21360472.

The previous prime is 21370829. The next prime is 21370847. The reversal of 21370831 is 13807312.

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 21370831 - 2¹ = 21370829 is a prime.

It is a super-2 number, since 2×21370831² = 913424835261122, 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 = 21370796 and 21370805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21370891) 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, 916 + ... + 6601.

It is an arithmetic number, because the mean of its divisors is an integer number (5345298).

Almost surely, 2^21370831 is an apocalyptic number.

21370831 is a deficient number, since it is larger than the sum of its proper divisors (10361).

21370831 is an equidigital number, since it uses as much as digits as its factorization.

21370831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10360.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21370831 is about 4622.8596128371. The cubic root of 21370831 is about 277.5069110634.

It can be divided in two parts, 21370 and 831, that added together give a square (22201 = 149²).

The spelling of 21370831 in words is "twenty-one million, three hundred seventy thousand, eight hundred thirty-one".