64691621 has 2 divisors, whose sum is σ = 64691622. Its totient is φ = 64691620.

The previous prime is 64691593. The next prime is 64691623. The reversal of 64691621 is 12619646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53728900 + 10962721 = 7330^2 + 3311^2 .

It is a cyclic number.

It is not a de Polignac number, because 64691621 - 2¹⁰ = 64690597 is a prime.

Together with 64691623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64691623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32345810 + 32345811.

It is an arithmetic number, because the mean of its divisors is an integer number (32345811).

Almost surely, 2^64691621 is an apocalyptic number.

It is an amenable number.

64691621 is a deficient number, since it is larger than the sum of its proper divisors (1).

64691621 is an equidigital number, since it uses as much as digits as its factorization.

64691621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 35.

The square root of 64691621 is about 8043.1101571469. The cubic root of 64691621 is about 401.4357177045.

The spelling of 64691621 in words is "sixty-four million, six hundred ninety-one thousand, six hundred twenty-one".