31491720 has 128 divisors (see below), whose sum is σ = 113097600. Its totient is φ = 7748352.

The previous prime is 31491697. The next prime is 31491727. The reversal of 31491720 is 2719413.

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

It is not an unprimeable number, because it can be changed into a prime (31491727) 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, 12919 + ... + 15161.

It is an arithmetic number, because the mean of its divisors is an integer number (883575).

Almost surely, 2^31491720 is an apocalyptic number.

31491720 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 31491720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (56548800).

31491720 is an abundant number, since it is smaller than the sum of its proper divisors (81605880).

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

31491720 is a wasteful number, since it uses less digits than its factorization.

31491720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2276 (or 2266 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 31491720 is about 5611.7483906533. The cubic root of 31491720 is about 315.7903057873.

The spelling of 31491720 in words is "thirty-one million, four hundred ninety-one thousand, seven hundred twenty".