31875181847721 has 9 divisors (see below), whose sum is σ = 46041953800791. Its totient is φ = 21250109940192.

The previous prime is 31875181847689. The next prime is 31875181847731. The reversal of 31875181847721 is 12774818157813.

It is a happy number.

The square root of 31875181847721 is 5645811.

It is a perfect power (a square), and thus also a powerful number.

31875181847721 is a `hidden beast` number, since 3 + 1 + 8 + 7 + 518 + 1 + 8 + 47 + 72 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 21776362245225 + 10098819602496 = 4666515^2 + 3177864^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 31875181847721 - 2⁵ = 31875181847689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31875181847731) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 15996465 + ... + 17878401.

Almost surely, 2^{31875181847721} is an apocalyptic number.

31875181847721 is the 5645811-st square number.

31875181847721 is the 2822906-th centered octagonal number.

It is an amenable number.

31875181847721 is a deficient number, since it is larger than the sum of its proper divisors (14166771953070).

31875181847721 is an frugal number, since it uses more digits than its factorization.

31875181847721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3763880 (or 1881940 counting only the distinct ones).

The product of its digits is 21073920, while the sum is 63.

The spelling of 31875181847721 in words is "thirty-one trillion, eight hundred seventy-five billion, one hundred eighty-one million, eight hundred forty-seven thousand, seven hundred twenty-one".