31518421728 has 48 divisors (see below), whose sum is σ = 82785039120. Its totient is φ = 10499895296.

The previous prime is 31518421721. The next prime is 31518421747. The reversal of 31518421728 is 82712481513.

It is a tau number, because it is divible by the number of its divisors (48).

It is a self number, because there is not a number n which added to its sum of digits gives 31518421728.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31518421721) 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, 66178 + ... + 259646.

It is an arithmetic number, because the mean of its divisors is an integer number (1724688315).

Almost surely, 2^31518421728 is an apocalyptic number.

It is an amenable number.

31518421728 is an abundant number, since it is smaller than the sum of its proper divisors (51266617392).

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

31518421728 is a wasteful number, since it uses less digits than its factorization.

31518421728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195179 (or 195171 counting only the distinct ones).

The product of its digits is 107520, while the sum is 42.

The spelling of 31518421728 in words is "thirty-one billion, five hundred eighteen million, four hundred twenty-one thousand, seven hundred twenty-eight".