721621406 has 64 divisors (see below), whose sum is σ = 1325963520. Its totient is φ = 290280960.

The previous prime is 721621393. The next prime is 721621421. The reversal of 721621406 is 604126127.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1229045 + ... + 1229631.

It is an arithmetic number, because the mean of its divisors is an integer number (20718180).

Almost surely, 2^721621406 is an apocalyptic number.

721621406 is a deficient number, since it is larger than the sum of its proper divisors (604342114).

721621406 is a wasteful number, since it uses less digits than its factorization.

721621406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 809.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 721621406 is about 26863.0118564542. The cubic root of 721621406 is about 896.9532390333.

The spelling of 721621406 in words is "seven hundred twenty-one million, six hundred twenty-one thousand, four hundred six".