857145721 has 16 divisors (see below), whose sum is σ = 909792000. Its totient is φ = 806205568.

The previous prime is 857145697. The next prime is 857145743. The reversal of 857145721 is 127541758.

It is not a de Polignac number, because 857145721 - 2¹¹ = 857143673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (857145781) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 316230 + ... + 318928.

It is an arithmetic number, because the mean of its divisors is an integer number (56862000).

Almost surely, 2^857145721 is an apocalyptic number.

It is an amenable number.

857145721 is a deficient number, since it is larger than the sum of its proper divisors (52646279).

857145721 is a wasteful number, since it uses less digits than its factorization.

857145721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3008.

The product of its digits is 78400, while the sum is 40.

The square root of 857145721 is about 29277.0510980870. The cubic root of 857145721 is about 949.9153095324.

The spelling of 857145721 in words is "eight hundred fifty-seven million, one hundred forty-five thousand, seven hundred twenty-one".