661942901 has 2 divisors, whose sum is σ = 661942902. Its totient is φ = 661942900.

The previous prime is 661942873. The next prime is 661942933. The reversal of 661942901 is 109249166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 593896900 + 68046001 = 24370^2 + 8249^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661942901 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 (661942201) 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, 330971450 + 330971451.

It is an arithmetic number, because the mean of its divisors is an integer number (330971451).

Almost surely, 2^661942901 is an apocalyptic number.

It is an amenable number.

661942901 is a deficient number, since it is larger than the sum of its proper divisors (1).

661942901 is an equidigital number, since it uses as much as digits as its factorization.

661942901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 661942901 is about 25728.2510287816. The cubic root of 661942901 is about 871.5122774982.

The spelling of 661942901 in words is "six hundred sixty-one million, nine hundred forty-two thousand, nine hundred one".