661265401 has 4 divisors (see below), whose sum is σ = 662054400. Its totient is φ = 660476404.

The previous prime is 661265383. The next prime is 661265447. The reversal of 661265401 is 104562166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 104562166 = 2 ⋅52281083.

It is a cyclic number.

It is not a de Polignac number, because 661265401 - 2⁹ = 661264889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661365401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 393241 + ... + 394918.

It is an arithmetic number, because the mean of its divisors is an integer number (165513600).

Almost surely, 2^661265401 is an apocalyptic number.

It is an amenable number.

661265401 is a deficient number, since it is larger than the sum of its proper divisors (788999).

661265401 is an equidigital number, since it uses as much as digits as its factorization.

661265401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 788998.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 661265401 is about 25715.0811976163. The cubic root of 661265401 is about 871.2148444297.

The spelling of 661265401 in words is "six hundred sixty-one million, two hundred sixty-five thousand, four hundred one".