138721972 has 12 divisors (see below), whose sum is σ = 257043780. Its totient is φ = 65280896.

The previous prime is 138721951. The next prime is 138721987. The reversal of 138721972 is 279127831.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 47251876 + 91470096 = 6874^2 + 9564^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1019947 + ... + 1020082.

It is an arithmetic number, because the mean of its divisors is an integer number (21420315).

Almost surely, 2^138721972 is an apocalyptic number.

It is an amenable number.

138721972 is a deficient number, since it is larger than the sum of its proper divisors (118321808).

138721972 is a wasteful number, since it uses less digits than its factorization.

138721972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2040050 (or 2040048 counting only the distinct ones).

The product of its digits is 42336, while the sum is 40.

The square root of 138721972 is about 11778.0292069599. The cubic root of 138721972 is about 517.6645413284.

The spelling of 138721972 in words is "one hundred thirty-eight million, seven hundred twenty-one thousand, nine hundred seventy-two".