661550653 has 2 divisors, whose sum is σ = 661550654. Its totient is φ = 661550652.

The previous prime is 661550651. The next prime is 661550671. The reversal of 661550653 is 356055166.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 533702404 + 127848249 = 23102^2 + 11307^2 .

It is a cyclic number.

It is not a de Polignac number, because 661550653 - 2¹ = 661550651 is a prime.

Together with 661550651, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661550651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330775326 + 330775327.

It is an arithmetic number, because the mean of its divisors is an integer number (330775327).

Almost surely, 2^661550653 is an apocalyptic number.

It is an amenable number.

661550653 is a deficient number, since it is larger than the sum of its proper divisors (1).

661550653 is an equidigital number, since it uses as much as digits as its factorization.

661550653 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81000, while the sum is 37.

The square root of 661550653 is about 25720.6269946905. The cubic root of 661550653 is about 871.3400992571.

The spelling of 661550653 in words is "six hundred sixty-one million, five hundred fifty thousand, six hundred fifty-three".