31897440 has 144 divisors (see below), whose sum is σ = 115341408. Its totient is φ = 7999488.

The previous prime is 31897421. The next prime is 31897451. The reversal of 31897440 is 4479813.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 31897395 and 31897404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 23829 + ... + 25131.

It is an arithmetic number, because the mean of its divisors is an integer number (800982).

Almost surely, 2^31897440 is an apocalyptic number.

31897440 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 31897440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (57670704).

31897440 is an abundant number, since it is smaller than the sum of its proper divisors (83443968).

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

31897440 is a wasteful number, since it uses less digits than its factorization.

31897440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1341 (or 1330 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 31897440 is about 5647.7818654760. The cubic root of 31897440 is about 317.1406727040.

The spelling of 31897440 in words is "thirty-one million, eight hundred ninety-seven thousand, four hundred forty".