721428681 has 4 divisors (see below), whose sum is σ = 961904912. Its totient is φ = 480952452.

The previous prime is 721428667. The next prime is 721428691. The reversal of 721428681 is 186824127.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 721428681 - 2¹³ = 721420489 is a prime.

It is a super-2 number, since 2×721428681² = 1040918683538799522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721428691) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 120238111 + ... + 120238116.

It is an arithmetic number, because the mean of its divisors is an integer number (240476228).

Almost surely, 2^721428681 is an apocalyptic number.

It is an amenable number.

721428681 is a deficient number, since it is larger than the sum of its proper divisors (240476231).

721428681 is a wasteful number, since it uses less digits than its factorization.

721428681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240476230.

The product of its digits is 43008, while the sum is 39.

The square root of 721428681 is about 26859.4244353821. The cubic root of 721428681 is about 896.8733815055.

The spelling of 721428681 in words is "seven hundred twenty-one million, four hundred twenty-eight thousand, six hundred eighty-one".