66256621 has 2 divisors, whose sum is σ = 66256622. Its totient is φ = 66256620.

The previous prime is 66256607. The next prime is 66256627. The reversal of 66256621 is 12665266.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64979721 + 1276900 = 8061^2 + 1130^2 .

It is a cyclic number.

It is not a de Polignac number, because 66256621 - 2⁹ = 66256109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66256627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33128310 + 33128311.

It is an arithmetic number, because the mean of its divisors is an integer number (33128311).

Almost surely, 2^66256621 is an apocalyptic number.

It is an amenable number.

66256621 is a deficient number, since it is larger than the sum of its proper divisors (1).

66256621 is an equidigital number, since it uses as much as digits as its factorization.

66256621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 34.

The square root of 66256621 is about 8139.8170126852. The cubic root of 66256621 is about 404.6470959230.

The spelling of 66256621 in words is "sixty-six million, two hundred fifty-six thousand, six hundred twenty-one".