1251815161 has 3 divisors (see below), whose sum is σ = 1251850543. Its totient is φ = 1251779780.

The previous prime is 1251815153. The next prime is 1251815207. The reversal of 1251815161 is 1615181521.

The square root of 1251815161 is 35381.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1615181521 = 257 ⋅6284753.

It can be written as a sum of positive squares in only one way, i.e., 1093558761 + 158256400 = 33069^2 + 12580^2 .

It is not a de Polignac number, because 1251815161 - 2³ = 1251815153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1251815141) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 17691 + ... + 53071.

Almost surely, 2^1251815161 is an apocalyptic number.

1251815161 is the 35381-st square number.

1251815161 is the 17691-st centered octagonal number.

It is an amenable number.

1251815161 is a deficient number, since it is larger than the sum of its proper divisors (35382).

1251815161 is an frugal number, since it uses more digits than its factorization.

1251815161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70762 (or 35381 counting only the distinct ones).

The product of its digits is 2400, while the sum is 31.

The cubic root of 1251815161 is about 1077.7385122735.

Adding to 1251815161 its reverse (1615181521), we get a palindrome (2866996682).

The spelling of 1251815161 in words is "one billion, two hundred fifty-one million, eight hundred fifteen thousand, one hundred sixty-one".