31120021 has 4 divisors (see below), whose sum is σ = 31168332. Its totient is φ = 31071712.

The previous prime is 31120009. The next prime is 31120027. The reversal of 31120021 is 12002113.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12002113 = 23 ⋅521831.

It can be written as a sum of positive squares in 2 ways, for example, as 15319396 + 15800625 = 3914^2 + 3975^2 .

It is a cyclic number.

It is not a de Polignac number, because 31120021 - 2¹⁵ = 31087253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31120027) 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, 23176 + ... + 24481.

It is an arithmetic number, because the mean of its divisors is an integer number (7792083).

Almost surely, 2^31120021 is an apocalyptic number.

It is an amenable number.

31120021 is a deficient number, since it is larger than the sum of its proper divisors (48311).

31120021 is an equidigital number, since it uses as much as digits as its factorization.

31120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48310.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 31120021 is about 5578.5321546084. The cubic root of 31120021 is about 314.5429535333.

Adding to 31120021 its reverse (12002113), we get a palindrome (43122134).

The spelling of 31120021 in words is "thirty-one million, one hundred twenty thousand, twenty-one".