31200021 has 6 divisors (see below), whose sum is σ = 45066710. Its totient is φ = 20800008.

The previous prime is 31200007. The next prime is 31200061. The reversal of 31200021 is 12000213.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 23415921 + 7784100 = 4839^2 + 2790^2 .

It is not a de Polignac number, because 31200021 - 2²¹ = 29102869 is a prime.

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: 3466669 = 31200021 / (3 + 1 + 2 + 0 + 0 + 0 + 2 + 1).

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 31199976 and 31200012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31200061) 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, 1733326 + ... + 1733343.

Almost surely, 2^31200021 is an apocalyptic number.

It is an amenable number.

31200021 is a deficient number, since it is larger than the sum of its proper divisors (13866689).

31200021 is a wasteful number, since it uses less digits than its factorization.

31200021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3466675 (or 3466672 counting only the distinct ones).

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

The square root of 31200021 is about 5585.6978973088. The cubic root of 31200021 is about 314.8122539572.

Adding to 31200021 its reverse (12000213), we get a palindrome (43200234).

It can be divided in two parts, 3 and 1200021, that multiplied together give a palindrome (3600063).

The spelling of 31200021 in words is "thirty-one million, two hundred thousand, twenty-one".