31122720 has 72 divisors (see below), whose sum is σ = 106211196. Its totient is φ = 8299008.

The previous prime is 31122719. The next prime is 31122727. The reversal of 31122720 is 2722113.

It can be written as a sum of positive squares in 2 ways, for example, as 28259856 + 2862864 = 5316^2 + 1692^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 31122693 and 31122702.

It is not an unprimeable number, because it can be changed into a prime (31122727) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9367 + ... + 12246.

Almost surely, 2^31122720 is an apocalyptic number.

31122720 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

31122720 is an abundant number, since it is smaller than the sum of its proper divisors (75088476).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

31122720 is a wasteful number, since it uses less digits than its factorization.

31122720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21634 (or 21623 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 31122720 is about 5578.7740588771. The cubic root of 31122720 is about 314.5520465744.

Adding to 31122720 its reverse (2722113), we get a palindrome (33844833).

It can be divided in two parts, 3112 and 2720, that added together give a cube (5832 = 18³).

The spelling of 31122720 in words is "thirty-one million, one hundred twenty-two thousand, seven hundred twenty".