1656121251 has 16 divisors (see below), whose sum is σ = 2224950944. Its totient is φ = 1095704064.

The previous prime is 1656121223. The next prime is 1656121261. The reversal of 1656121251 is 1521216561.

It is not a de Polignac number, because 1656121251 - 2⁷ = 1656121123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1656121261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 513195 + ... + 516411.

It is an arithmetic number, because the mean of its divisors is an integer number (139059434).

Almost surely, 2^1656121251 is an apocalyptic number.

1656121251 is a deficient number, since it is larger than the sum of its proper divisors (568829693).

1656121251 is a wasteful number, since it uses less digits than its factorization.

1656121251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4470.

The product of its digits is 3600, while the sum is 30.

The square root of 1656121251 is about 40695.4696618678. The cubic root of 1656121251 is about 1183.1252143591.

The spelling of 1656121251 in words is "one billion, six hundred fifty-six million, one hundred twenty-one thousand, two hundred fifty-one".