3121621109721 has 9 divisors (see below), whose sum is σ = 4509015925791. Its totient is φ = 2081077206192.

The previous prime is 3121621109687. The next prime is 3121621109731. The reversal of 3121621109721 is 1279011261213.

It is a happy number.

The square root of 3121621109721 is 1766811.

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

3121621109721 is a `hidden beast` number, since 3 + 1 + 2 + 1 + 621 + 1 + 0 + 9 + 7 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 843743288025 + 2277877821696 = 918555^2 + 1509264^2 .

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

It is not a de Polignac number, because 3121621109721 - 2⁹ = 3121621109209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (3121621109731) 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, 5005965 + ... + 5594901.

Almost surely, 2^{3121621109721} is an apocalyptic number.

3121621109721 is the 1766811-st square number.

3121621109721 is the 883406-th centered octagonal number.

It is an amenable number.

3121621109721 is a deficient number, since it is larger than the sum of its proper divisors (1387394816070).

3121621109721 is an frugal number, since it uses more digits than its factorization.

3121621109721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1177880 (or 588940 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

Multiplying 3121621109721 by its sum of digits (36), we get a square (112378359949956 = 10600866²).

The spelling of 3121621109721 in words is "three trillion, one hundred twenty-one billion, six hundred twenty-one million, one hundred nine thousand, seven hundred twenty-one".