3121987561 has 16 divisors (see below), whose sum is σ = 3895170048. Its totient is φ = 2430954000.

The previous prime is 3121987553. The next prime is 3121987597. The reversal of 3121987561 is 1657891213.

It is a cyclic number.

It is not a de Polignac number, because 3121987561 - 2³ = 3121987553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (3121987511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 97756 + ... + 125698.

It is an arithmetic number, because the mean of its divisors is an integer number (243448128).

Almost surely, 2^3121987561 is an apocalyptic number.

It is an amenable number.

3121987561 is a deficient number, since it is larger than the sum of its proper divisors (773182487).

3121987561 is a wasteful number, since it uses less digits than its factorization.

3121987561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29412.

The product of its digits is 90720, while the sum is 43.

The square root of 3121987561 is about 55874.7488674446. The cubic root of 3121987561 is about 1461.5389354013.

The spelling of 3121987561 in words is "three billion, one hundred twenty-one million, nine hundred eighty-seven thousand, five hundred sixty-one".