689640121 has 3 divisors (see below), whose sum is σ = 689666383. Its totient is φ = 689613860.

The previous prime is 689640089. The next prime is 689640137. The reversal of 689640121 is 121046986.

It is a happy number.

The square root of 689640121 is 26261.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 4247721 + 685392400 = 2061^2 + 26180^2 .

It is not a de Polignac number, because 689640121 - 2⁵ = 689640089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (689640181) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 13131 + ... + 39391.

Almost surely, 2^689640121 is an apocalyptic number.

689640121 is the 26261-st square number.

689640121 is the 13131-st centered octagonal number.

It is an amenable number.

689640121 is a deficient number, since it is larger than the sum of its proper divisors (26262).

689640121 is an frugal number, since it uses more digits than its factorization.

689640121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52522 (or 26261 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 37.

The cubic root of 689640121 is about 883.5019379436.

Multiplying 689640121 by its product of nonzero digits (20736), we get a square (14300377549056 = 3781584²).

The spelling of 689640121 in words is "six hundred eighty-nine million, six hundred forty thousand, one hundred twenty-one".