645642261 has 24 divisors (see below), whose sum is σ = 1018371744. Its totient is φ = 390915360.

The previous prime is 645642259. The next prime is 645642271. The reversal of 645642261 is 162246546.

645642261 is a `hidden beast` number, since 6 + 4 + 5 + 642 + 2 + 6 + 1 = 666.

It is not a de Polignac number, because 645642261 - 2¹ = 645642259 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645642241) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 123870 + ... + 128976.

It is an arithmetic number, because the mean of its divisors is an integer number (42432156).

Almost surely, 2^645642261 is an apocalyptic number.

It is an amenable number.

645642261 is a deficient number, since it is larger than the sum of its proper divisors (372729483).

645642261 is a wasteful number, since it uses less digits than its factorization.

645642261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6401 (or 6398 counting only the distinct ones).

The product of its digits is 69120, while the sum is 36.

The square root of 645642261 is about 25409.4915533546. The cubic root of 645642261 is about 864.2989457099.

The spelling of 645642261 in words is "six hundred forty-five million, six hundred forty-two thousand, two hundred sixty-one".