3161781221 has 4 divisors (see below), whose sum is σ = 3168823500. Its totient is φ = 3154738944.

The previous prime is 3161781187. The next prime is 3161781229. The reversal of 3161781221 is 1221871613.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1221871613 = 193 ⋅6330941.

It can be written as a sum of positive squares in 2 ways, for example, as 2013316900 + 1148464321 = 44870^2 + 33889^2 .

It is a cyclic number.

It is not a de Polignac number, because 3161781221 - 2¹⁰ = 3161780197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3161781229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3520466 + ... + 3521363.

It is an arithmetic number, because the mean of its divisors is an integer number (792205875).

Almost surely, 2^3161781221 is an apocalyptic number.

It is an amenable number.

3161781221 is a deficient number, since it is larger than the sum of its proper divisors (7042279).

3161781221 is an equidigital number, since it uses as much as digits as its factorization.

3161781221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7042278.

The product of its digits is 4032, while the sum is 32.

The square root of 3161781221 is about 56229.7183080264. The cubic root of 3161781221 is about 1467.7224547190.

The spelling of 3161781221 in words is "three billion, one hundred sixty-one million, seven hundred eighty-one thousand, two hundred twenty-one".