643625621 has 2 divisors, whose sum is σ = 643625622. Its totient is φ = 643625620.

The previous prime is 643625617. The next prime is 643625657. The reversal of 643625621 is 126526346.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 462723121 + 180902500 = 21511^2 + 13450^2 .

It is a cyclic number.

It is not a de Polignac number, because 643625621 - 2² = 643625617 is a prime.

It is a super-3 number, since 3×643625621³ (a number of 27 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643625821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321812810 + 321812811.

It is an arithmetic number, because the mean of its divisors is an integer number (321812811).

Almost surely, 2^643625621 is an apocalyptic number.

It is an amenable number.

643625621 is a deficient number, since it is larger than the sum of its proper divisors (1).

643625621 is an equidigital number, since it uses as much as digits as its factorization.

643625621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 51840, while the sum is 35.

The square root of 643625621 is about 25369.7777089197. Note that the first 4 decimals coincide. The cubic root of 643625621 is about 863.3981384579.

The spelling of 643625621 in words is "six hundred forty-three million, six hundred twenty-five thousand, six hundred twenty-one".