721405660 has 48 divisors (see below), whose sum is σ = 1555212960. Its totient is φ = 280924160.

The previous prime is 721405651. The next prime is 721405721. The reversal of 721405660 is 66504127.

It is a happy number.

It is a super-2 number, since 2×721405660² = 1040852252560071200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 761307 + ... + 762253.

It is an arithmetic number, because the mean of its divisors is an integer number (32400270).

Almost surely, 2^721405660 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721405660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (777606480).

721405660 is an abundant number, since it is smaller than the sum of its proper divisors (833807300).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721405660 is a wasteful number, since it uses less digits than its factorization.

721405660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1926 (or 1924 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 721405660 is about 26858.9958859225. The cubic root of 721405660 is about 896.8638415735.

Adding to 721405660 its reverse (66504127), we get a palindrome (787909787).

The spelling of 721405660 in words is "seven hundred twenty-one million, four hundred five thousand, six hundred sixty".