721835689 has 9 divisors (see below), whose sum is σ = 734602071. Its totient is φ = 709288800.

The previous prime is 721835671. The next prime is 721835693. The reversal of 721835689 is 986538127.

The square root of 721835689 is 26867.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 714653289 + 7182400 = 26733^2 + 2680^2 .

It is a de Polignac number, because none of the positive numbers 2^k-721835689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721835659) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1799889 + ... + 1800289.

Almost surely, 2^721835689 is an apocalyptic number.

721835689 is the 26867-th square number.

721835689 is the 13434-th centered octagonal number.

It is an amenable number.

721835689 is a deficient number, since it is larger than the sum of its proper divisors (12766382).

721835689 is an frugal number, since it uses more digits than its factorization.

721835689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 936 (or 468 counting only the distinct ones).

The product of its digits is 725760, while the sum is 49.

The cubic root of 721835689 is about 897.0420126422.

Multiplying 721835689 by its sum of digits (49), we get a square (35369948761 = 188069²).

The spelling of 721835689 in words is "seven hundred twenty-one million, eight hundred thirty-five thousand, six hundred eighty-nine".