721644001 has 8 divisors (see below), whose sum is σ = 779964584. Its totient is φ = 663724800.

The previous prime is 721643987. The next prime is 721644019. The reversal of 721644001 is 100446127.

It can be written as a sum of positive squares in 4 ways, for example, as 2117025 + 719526976 = 1455^2 + 26824^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721644001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721644061) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 96600 + ... + 103801.

It is an arithmetic number, because the mean of its divisors is an integer number (97495573).

Almost surely, 2^721644001 is an apocalyptic number.

It is an amenable number.

721644001 is a deficient number, since it is larger than the sum of its proper divisors (58320583).

721644001 is a wasteful number, since it uses less digits than its factorization.

721644001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200691.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 721644001 is about 26863.4324128545. The cubic root of 721644001 is about 896.9626005659.

The spelling of 721644001 in words is "seven hundred twenty-one million, six hundred forty-four thousand, one".