664558621 has 2 divisors, whose sum is σ = 664558622. Its totient is φ = 664558620.

The previous prime is 664558613. The next prime is 664558663. The reversal of 664558621 is 126855466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 369062521 + 295496100 = 19211^2 + 17190^2 .

It is a cyclic number.

It is not a de Polignac number, because 664558621 - 2³ = 664558613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664558121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332279310 + 332279311.

It is an arithmetic number, because the mean of its divisors is an integer number (332279311).

Almost surely, 2^664558621 is an apocalyptic number.

It is an amenable number.

664558621 is a deficient number, since it is larger than the sum of its proper divisors (1).

664558621 is an equidigital number, since it uses as much as digits as its factorization.

664558621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 345600, while the sum is 43.

The square root of 664558621 is about 25779.0345242020. The cubic root of 664558621 is about 872.6587187546.

It can be divided in two parts, 66455 and 8621, that added together give a square (75076 = 274²).

The spelling of 664558621 in words is "six hundred sixty-four million, five hundred fifty-eight thousand, six hundred twenty-one".