661237609 has 2 divisors, whose sum is σ = 661237610. Its totient is φ = 661237608.

The previous prime is 661237597. The next prime is 661237631. The reversal of 661237609 is 906732166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 656384400 + 4853209 = 25620^2 + 2203^2 .

It is a cyclic number.

It is not a de Polignac number, because 661237609 - 2¹⁹ = 660713321 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661237009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330618804 + 330618805.

It is an arithmetic number, because the mean of its divisors is an integer number (330618805).

Almost surely, 2^661237609 is an apocalyptic number.

It is an amenable number.

661237609 is a deficient number, since it is larger than the sum of its proper divisors (1).

661237609 is an equidigital number, since it uses as much as digits as its factorization.

661237609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81648, while the sum is 40.

The square root of 661237609 is about 25714.5408086553. The cubic root of 661237609 is about 871.2026389712.

The spelling of 661237609 in words is "six hundred sixty-one million, two hundred thirty-seven thousand, six hundred nine".