31721420 has 24 divisors (see below), whose sum is σ = 67530624. Its totient is φ = 12514176.

The previous prime is 31721419. The next prime is 31721429. The reversal of 31721420 is 2412713.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 31721392 and 31721401.

It is not an unprimeable number, because it can be changed into a prime (31721429) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9404 + ... + 12323.

It is an arithmetic number, because the mean of its divisors is an integer number (2813776).

Almost surely, 2^31721420 is an apocalyptic number.

It is an amenable number.

31721420 is an abundant number, since it is smaller than the sum of its proper divisors (35809204).

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

31721420 is a wasteful number, since it uses less digits than its factorization.

31721420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21809 (or 21807 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 31721420 is about 5632.1771989170. The cubic root of 31721420 is about 316.5562360402.

The spelling of 31721420 in words is "thirty-one million, seven hundred twenty-one thousand, four hundred twenty".