1251164561 has 4 divisors (see below), whose sum is σ = 1272370800. Its totient is φ = 1229958324.

The previous prime is 1251164549. The next prime is 1251164591. The reversal of 1251164561 is 1654611521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1654611521 = 233 ⋅7101337.

It is a cyclic number.

It is not a de Polignac number, because 1251164561 - 2³⁰ = 177422737 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1251164531) 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, 10603031 + ... + 10603148.

It is an arithmetic number, because the mean of its divisors is an integer number (318092700).

Almost surely, 2^1251164561 is an apocalyptic number.

It is an amenable number.

1251164561 is a deficient number, since it is larger than the sum of its proper divisors (21206239).

1251164561 is an equidigital number, since it uses as much as digits as its factorization.

1251164561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21206238.

The product of its digits is 7200, while the sum is 32.

The square root of 1251164561 is about 35371.8046047979. The cubic root of 1251164561 is about 1077.5517705973.

The spelling of 1251164561 in words is "one billion, two hundred fifty-one million, one hundred sixty-four thousand, five hundred sixty-one".