721428639 has 16 divisors (see below), whose sum is σ = 979353984. Its totient is φ = 472255200.

The previous prime is 721428637. The next prime is 721428667. The reversal of 721428639 is 936824127.

It is not a de Polignac number, because 721428639 - 2¹ = 721428637 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 721428639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721428637) 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, 114604 + ... + 120734.

It is an arithmetic number, because the mean of its divisors is an integer number (61209624).

Almost surely, 2^721428639 is an apocalyptic number.

721428639 is a deficient number, since it is larger than the sum of its proper divisors (257925345).

721428639 is a wasteful number, since it uses less digits than its factorization.

721428639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6838.

The product of its digits is 145152, while the sum is 42.

The square root of 721428639 is about 26859.4236535336. The cubic root of 721428639 is about 896.8733641008.

It can be divided in two parts, 7214 and 28639, that added together give a palindrome (35853).

The spelling of 721428639 in words is "seven hundred twenty-one million, four hundred twenty-eight thousand, six hundred thirty-nine".