664841554021 has 2 divisors, whose sum is σ = 664841554022. Its totient is φ = 664841554020.

The previous prime is 664841554001. The next prime is 664841554031. The reversal of 664841554021 is 120455148466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 489774625921 + 175066928100 = 699839^2 + 418410^2 .

It is a cyclic number.

It is not a de Polignac number, because 664841554021 - 2³⁵ = 630481815653 is a prime.

It is a super-2 number, since 2×664841554021² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664841554001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332420777010 + 332420777011.

It is an arithmetic number, because the mean of its divisors is an integer number (332420777011).

Almost surely, 2^664841554021 is an apocalyptic number.

It is an amenable number.

664841554021 is a deficient number, since it is larger than the sum of its proper divisors (1).

664841554021 is an equidigital number, since it uses as much as digits as its factorization.

664841554021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 921600, while the sum is 46.

The spelling of 664841554021 in words is "six hundred sixty-four billion, eight hundred forty-one million, five hundred fifty-four thousand, twenty-one".