721556138 has 32 divisors (see below), whose sum is σ = 1151055360. Its totient is φ = 338532480.

The previous prime is 721556137. The next prime is 721556149. The reversal of 721556138 is 831655127.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (721556137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 657206 + ... + 658302.

It is an arithmetic number, because the mean of its divisors is an integer number (35970480).

Almost surely, 2^721556138 is an apocalyptic number.

721556138 is a deficient number, since it is larger than the sum of its proper divisors (429499222).

721556138 is a wasteful number, since it uses less digits than its factorization.

721556138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1382.

The product of its digits is 50400, while the sum is 38.

The square root of 721556138 is about 26861.7969987118. The cubic root of 721556138 is about 896.9261961783.

The spelling of 721556138 in words is "seven hundred twenty-one million, five hundred fifty-six thousand, one hundred thirty-eight".