1257157721 has 8 divisors (see below), whose sum is σ = 1282768704. Its totient is φ = 1231616880.

The previous prime is 1257157711. The next prime is 1257157729. The reversal of 1257157721 is 1277517521.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1257157721 - 2²⁶ = 1190048857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1257157729) 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 7 ways as a sum of consecutive naturals, for example, 19460 + ... + 53786.

It is an arithmetic number, because the mean of its divisors is an integer number (160346088).

Almost surely, 2^1257157721 is an apocalyptic number.

It is an amenable number.

1257157721 is a deficient number, since it is larger than the sum of its proper divisors (25610983).

1257157721 is an equidigital number, since it uses as much as digits as its factorization.

1257157721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35071.

The product of its digits is 34300, while the sum is 38.

The square root of 1257157721 is about 35456.4200251520. The cubic root of 1257157721 is about 1079.2695452223.

The spelling of 1257157721 in words is "one billion, two hundred fifty-seven million, one hundred fifty-seven thousand, seven hundred twenty-one".