691123621 has 4 divisors (see below), whose sum is σ = 714955500. Its totient is φ = 667291744.

The previous prime is 691123597. The next prime is 691123637. The reversal of 691123621 is 126321196.

691123621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 359519521 + 331604100 = 18961^2 + 18210^2 .

It is a cyclic number.

It is not a de Polignac number, because 691123621 - 2⁷ = 691123493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691123681) 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, 11915896 + ... + 11915953.

It is an arithmetic number, because the mean of its divisors is an integer number (178738875).

Almost surely, 2^691123621 is an apocalyptic number.

It is an amenable number.

691123621 is a deficient number, since it is larger than the sum of its proper divisors (23831879).

691123621 is a wasteful number, since it uses less digits than its factorization.

691123621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23831878.

The product of its digits is 3888, while the sum is 31.

The square root of 691123621 is about 26289.2301332694. The cubic root of 691123621 is about 884.1349910386.

The spelling of 691123621 in words is "six hundred ninety-one million, one hundred twenty-three thousand, six hundred twenty-one".