31720721478 has 32 divisors (see below), whose sum is σ = 65716738560. Its totient is φ = 10195332000.

The previous prime is 31720721477. The next prime is 31720721497. The reversal of 31720721478 is 87412702713.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31720721477) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9301 + ... + 252047.

It is an arithmetic number, because the mean of its divisors is an integer number (2053648080).

Almost surely, 2^31720721478 is an apocalyptic number.

31720721478 is an abundant number, since it is smaller than the sum of its proper divisors (33996017082).

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

31720721478 is a wasteful number, since it uses less digits than its factorization.

31720721478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243532.

The product of its (nonzero) digits is 131712, while the sum is 42.

The spelling of 31720721478 in words is "thirty-one billion, seven hundred twenty million, seven hundred twenty-one thousand, four hundred seventy-eight".