661576901 has 4 divisors (see below), whose sum is σ = 665232204. Its totient is φ = 657921600.

The previous prime is 661576897. The next prime is 661576939. The reversal of 661576901 is 109675166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 109675166 = 2 ⋅54837583.

It can be written as a sum of positive squares in 2 ways, for example, as 219484225 + 442092676 = 14815^2 + 21026^2 .

It is a cyclic number.

It is not a de Polignac number, because 661576901 - 2² = 661576897 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661576501) 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, 1827380 + ... + 1827741.

It is an arithmetic number, because the mean of its divisors is an integer number (166308051).

Almost surely, 2^661576901 is an apocalyptic number.

It is an amenable number.

661576901 is a deficient number, since it is larger than the sum of its proper divisors (3655303).

661576901 is a wasteful number, since it uses less digits than its factorization.

661576901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3655302.

The product of its (nonzero) digits is 68040, while the sum is 41.

The square root of 661576901 is about 25721.1372415762. The cubic root of 661576901 is about 871.3516230068.

The spelling of 661576901 in words is "six hundred sixty-one million, five hundred seventy-six thousand, nine hundred one".