661021373 has 2 divisors, whose sum is σ = 661021374. Its totient is φ = 661021372.

The previous prime is 661021369. The next prime is 661021399. The reversal of 661021373 is 373120166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 420988324 + 240033049 = 20518^2 + 15493^2 .

It is a cyclic number.

It is not a de Polignac number, because 661021373 - 2² = 661021369 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661021313) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330510686 + 330510687.

It is an arithmetic number, because the mean of its divisors is an integer number (330510687).

Almost surely, 2^661021373 is an apocalyptic number.

It is an amenable number.

661021373 is a deficient number, since it is larger than the sum of its proper divisors (1).

661021373 is an equidigital number, since it uses as much as digits as its factorization.

661021373 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4536, while the sum is 29.

The square root of 661021373 is about 25710.3359176810. The cubic root of 661021373 is about 871.1076625663.

The spelling of 661021373 in words is "six hundred sixty-one million, twenty-one thousand, three hundred seventy-three".