721561501 has 8 divisors (see below), whose sum is σ = 740847744. Its totient is φ = 702355680.

The previous prime is 721561483. The next prime is 721561507. The reversal of 721561501 is 105165127.

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 721561501 - 2²⁵ = 688007069 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721561501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721561507) 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, 1701 + ... + 38026.

It is an arithmetic number, because the mean of its divisors is an integer number (92605968).

Almost surely, 2^721561501 is an apocalyptic number.

It is an amenable number.

721561501 is a deficient number, since it is larger than the sum of its proper divisors (19286243).

721561501 is a wasteful number, since it uses less digits than its factorization.

721561501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40211.

The product of its (nonzero) digits is 2100, while the sum is 28.

The square root of 721561501 is about 26861.8968243123. The cubic root of 721561501 is about 896.9284183216.

The spelling of 721561501 in words is "seven hundred twenty-one million, five hundred sixty-one thousand, five hundred one".