661240645001 has 2 divisors, whose sum is σ = 661240645002. Its totient is φ = 661240645000.

The previous prime is 661240644949. The next prime is 661240645019. The reversal of 661240645001 is 100546042166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 655330725625 + 5909919376 = 809525^2 + 76876^2 .

It is a cyclic number.

It is not a de Polignac number, because 661240645001 - 2¹⁸ = 661240382857 is a prime.

It is not a weakly prime, because it can be changed into another prime (661240645081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330620322500 + 330620322501.

It is an arithmetic number, because the mean of its divisors is an integer number (330620322501).

Almost surely, 2^661240645001 is an apocalyptic number.

It is an amenable number.

661240645001 is a deficient number, since it is larger than the sum of its proper divisors (1).

661240645001 is an equidigital number, since it uses as much as digits as its factorization.

661240645001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 35.

Adding to 661240645001 its reverse (100546042166), we get a palindrome (761786687167).

The spelling of 661240645001 in words is "six hundred sixty-one billion, two hundred forty million, six hundred forty-five thousand, one".