2151981561 has 8 divisors (see below), whose sum is σ = 2869730560. Its totient is φ = 1434443472.

The previous prime is 2151981551. The next prime is 2151981563. The reversal of 2151981561 is 1651891512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 2151981561 - 2⁹ = 2151981049 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2151981563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27145 + ... + 70998.

It is an arithmetic number, because the mean of its divisors is an integer number (358716320).

Almost surely, 2^2151981561 is an apocalyptic number.

It is an amenable number.

2151981561 is a deficient number, since it is larger than the sum of its proper divisors (717748999).

2151981561 is an equidigital number, since it uses as much as digits as its factorization.

2151981561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105455.

The product of its digits is 21600, while the sum is 39.

The square root of 2151981561 is about 46389.4552781125. The cubic root of 2151981561 is about 1291.0592747686.

The spelling of 2151981561 in words is "two billion, one hundred fifty-one million, nine hundred eighty-one thousand, five hundred sixty-one".