661960261 has 4 divisors (see below), whose sum is σ = 662373792. Its totient is φ = 661546732.

The previous prime is 661960253. The next prime is 661960279. The reversal of 661960261 is 162069166.

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.

It is a cyclic number.

It is not a de Polignac number, because 661960261 - 2³ = 661960253 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 661960261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661960241) 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, 204355 + ... + 207568.

It is an arithmetic number, because the mean of its divisors is an integer number (165593448).

Almost surely, 2^661960261 is an apocalyptic number.

It is an amenable number.

661960261 is a deficient number, since it is larger than the sum of its proper divisors (413531).

661960261 is a wasteful number, since it uses less digits than its factorization.

661960261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 413530.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 661960261 is about 25728.5883988998. The cubic root of 661960261 is about 871.5198961417.

The spelling of 661960261 in words is "six hundred sixty-one million, nine hundred sixty thousand, two hundred sixty-one".