31561920 has 224 divisors, whose sum is σ = 120335040. Its totient is φ = 7741440.

The previous prime is 31561919. The next prime is 31561927. The reversal of 31561920 is 2916513.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31561927) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 112180 + ... + 112460.

It is an arithmetic number, because the mean of its divisors is an integer number (537210).

Almost surely, 2^31561920 is an apocalyptic number.

31561920 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31561920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (60167520).

31561920 is an abundant number, since it is smaller than the sum of its proper divisors (88773120).

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

31561920 is a wasteful number, since it uses less digits than its factorization.

31561920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320 (or 304 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 31561920 is about 5617.9996440014. Note that the first 3 decimals coincide. The cubic root of 31561920 is about 316.0247804099.

The spelling of 31561920 in words is "thirty-one million, five hundred sixty-one thousand, nine hundred twenty".