857507921 has 4 divisors (see below), whose sum is σ = 861353472. Its totient is φ = 853662372.

The previous prime is 857507909. The next prime is 857507929. The reversal of 857507921 is 129705758.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-857507921 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (857507929) 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, 1922441 + ... + 1922886.

It is an arithmetic number, because the mean of its divisors is an integer number (215338368).

Almost surely, 2^857507921 is an apocalyptic number.

It is an amenable number.

857507921 is a deficient number, since it is larger than the sum of its proper divisors (3845551).

857507921 is a wasteful number, since it uses less digits than its factorization.

857507921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3845550.

The product of its (nonzero) digits is 176400, while the sum is 44.

The square root of 857507921 is about 29283.2361770348. The cubic root of 857507921 is about 950.0490910920.

The spelling of 857507921 in words is "eight hundred fifty-seven million, five hundred seven thousand, nine hundred twenty-one".