21310031 has 4 divisors (see below), whose sum is σ = 21378864. Its totient is φ = 21241200.

The previous prime is 21310021. The next prime is 21310043. The reversal of 21310031 is 13001312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21310031 - 2¹⁴ = 21293647 is a prime.

It is a super-2 number, since 2×21310031² = 908234842441922, 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 = 21309994 and 21310021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21310021) 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, 33950 + ... + 34571.

It is an arithmetic number, because the mean of its divisors is an integer number (5344716).

Almost surely, 2^21310031 is an apocalyptic number.

21310031 is a deficient number, since it is larger than the sum of its proper divisors (68833).

21310031 is an equidigital number, since it uses as much as digits as its factorization.

21310031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68832.

The product of its (nonzero) digits is 18, while the sum is 11.

The square root of 21310031 is about 4616.2789127175. The cubic root of 21310031 is about 277.2434921038.

Adding to 21310031 its reverse (13001312), we get a palindrome (34311343).

The spelling of 21310031 in words is "twenty-one million, three hundred ten thousand, thirty-one".