400175721 has 20 divisors (see below), whose sum is σ = 652139664. Its totient is φ = 242530200.

The previous prime is 400175717. The next prime is 400175723. The reversal of 400175721 is 127571004.

It is not a de Polignac number, because 400175721 - 2² = 400175717 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (400175723) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 223675 + ... + 225456.

Almost surely, 2^400175721 is an apocalyptic number.

It is an amenable number.

400175721 is a deficient number, since it is larger than the sum of its proper divisors (251963943).

400175721 is a wasteful number, since it uses less digits than its factorization.

400175721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 449154 (or 449145 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 400175721 is about 20004.3925426392. The cubic root of 400175721 is about 736.9141775491.

It can be divided in two parts, 400 and 175721, that added together give a triangular number (176121 = T₅₉₃).

The spelling of 400175721 in words is "four hundred million, one hundred seventy-five thousand, seven hundred twenty-one".