1215257491 has 4 divisors (see below), whose sum is σ = 1388865712. Its totient is φ = 1041649272.

The previous prime is 1215257473. The next prime is 1215257573. The reversal of 1215257491 is 1947525121.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1215257491 - 2⁷ = 1215257363 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1215257491.

It is not an unprimeable number, because it can be changed into a prime (1215257411) 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 3 ways as a sum of consecutive naturals, for example, 86804100 + ... + 86804113.

It is an arithmetic number, because the mean of its divisors is an integer number (347216428).

Almost surely, 2^1215257491 is an apocalyptic number.

1215257491 is a deficient number, since it is larger than the sum of its proper divisors (173608221).

1215257491 is an equidigital number, since it uses as much as digits as its factorization.

1215257491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173608220.

The product of its digits is 25200, while the sum is 37.

The square root of 1215257491 is about 34860.5434696592. The cubic root of 1215257491 is about 1067.1433661061.

The spelling of 1215257491 in words is "one billion, two hundred fifteen million, two hundred fifty-seven thousand, four hundred ninety-one".