665520637 has 2 divisors, whose sum is σ = 665520638. Its totient is φ = 665520636.

The previous prime is 665520631. The next prime is 665520659. The reversal of 665520637 is 736025566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 544102276 + 121418361 = 23326^2 + 11019^2 .

It is a cyclic number.

It is not a de Polignac number, because 665520637 - 2⁷ = 665520509 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665520637.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665520631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332760318 + 332760319.

It is an arithmetic number, because the mean of its divisors is an integer number (332760319).

Almost surely, 2^665520637 is an apocalyptic number.

It is an amenable number.

665520637 is a deficient number, since it is larger than the sum of its proper divisors (1).

665520637 is an equidigital number, since it uses as much as digits as its factorization.

665520637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 226800, while the sum is 40.

The square root of 665520637 is about 25797.6866598538. The cubic root of 665520637 is about 873.0796030610.

The spelling of 665520637 in words is "six hundred sixty-five million, five hundred twenty thousand, six hundred thirty-seven".