265640661 has 64 divisors (see below), whose sum is σ = 467389440. Its totient is φ = 146992320.

The previous prime is 265640659. The next prime is 265640689. The reversal of 265640661 is 166046562.

It is a happy number.

265640661 is a `hidden beast` number, since 2 + 6 + 5 + 640 + 6 + 6 + 1 = 666.

It is not a de Polignac number, because 265640661 - 2¹ = 265640659 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (265640651) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 412806 + ... + 413448.

It is an arithmetic number, because the mean of its divisors is an integer number (7302960).

Almost surely, 2^265640661 is an apocalyptic number.

It is an amenable number.

265640661 is a deficient number, since it is larger than the sum of its proper divisors (201748779).

265640661 is a wasteful number, since it uses less digits than its factorization.

265640661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 783 (or 777 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The square root of 265640661 is about 16298.4864634726. The cubic root of 265640661 is about 642.8330307782.

The spelling of 265640661 in words is "two hundred sixty-five million, six hundred forty thousand, six hundred sixty-one".