21200031 has 6 divisors (see below), whose sum is σ = 30622280. Its totient is φ = 14133348.

The previous prime is 21200021. The next prime is 21200041. The reversal of 21200031 is 13000212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21200021) and next prime (21200041).

It is not a de Polignac number, because 21200031 - 2⁵ = 21199999 is a prime.

It is a super-2 number, since 2×21200031² = 898882628801922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2355559 = 21200031 / (2 + 1 + 2 + 0 + 0 + 0 + 3 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21199986 and 21200022.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21200021) 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, 1177771 + ... + 1177788.

Almost surely, 2^21200031 is an apocalyptic number.

21200031 is a deficient number, since it is larger than the sum of its proper divisors (9422249).

21200031 is a wasteful number, since it uses less digits than its factorization.

21200031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2355565 (or 2355562 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

The square root of 21200031 is about 4604.3491396722. The cubic root of 21200031 is about 276.7656356302.

Adding to 21200031 its reverse (13000212), we get a palindrome (34200243).

It can be divided in two parts, 21 and 200031, that multiplied together give a triangular number (4200651 = T₂₈₉₈).

The spelling of 21200031 in words is "twenty-one million, two hundred thousand, thirty-one".