721405655 has 12 divisors (see below), whose sum is σ = 869379960. Its totient is φ = 574668864.

The previous prime is 721405651. The next prime is 721405721. The reversal of 721405655 is 556504127.

It is not a de Polignac number, because 721405655 - 2² = 721405651 is a prime.

It is a super-2 number, since 2×721405655² = 1040852238131958050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721405651) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1168907 + ... + 1169523.

It is an arithmetic number, because the mean of its divisors is an integer number (72448330).

Almost surely, 2^721405655 is an apocalyptic number.

721405655 is a deficient number, since it is larger than the sum of its proper divisors (147974305).

721405655 is an frugal number, since it uses more digits than its factorization.

721405655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1618 (or 1001 counting only the distinct ones).

The product of its (nonzero) digits is 42000, while the sum is 35.

The square root of 721405655 is about 26858.9957928438. The cubic root of 721405655 is about 896.8638395014.

The spelling of 721405655 in words is "seven hundred twenty-one million, four hundred five thousand, six hundred fifty-five".