623809721 has 2 divisors, whose sum is σ = 623809722. Its totient is φ = 623809720.

The previous prime is 623809717. The next prime is 623809723. The reversal of 623809721 is 127908326.

623809721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 359292025 + 264517696 = 18955^2 + 16264^2 .

It is a cyclic number.

It is not a de Polignac number, because 623809721 - 2² = 623809717 is a prime.

Together with 623809723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (623809723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 311904860 + 311904861.

It is an arithmetic number, because the mean of its divisors is an integer number (311904861).

Almost surely, 2^623809721 is an apocalyptic number.

It is an amenable number.

623809721 is a deficient number, since it is larger than the sum of its proper divisors (1).

623809721 is an equidigital number, since it uses as much as digits as its factorization.

623809721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36288, while the sum is 38.

The square root of 623809721 is about 24976.1830750817. The cubic root of 623809721 is about 854.4448688319. Note that the first 3 decimals are identical.

The spelling of 623809721 in words is "six hundred twenty-three million, eight hundred nine thousand, seven hundred twenty-one".