645261135521 has 16 divisors (see below), whose sum is σ = 649199073600. Its totient is φ = 641337860160.

The previous prime is 645261135487. The next prime is 645261135529. The reversal of 645261135521 is 125531162546.

645261135521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 645261135521 - 2¹⁸ = 645260873377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645261135529) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 290526191 + ... + 290528411.

It is an arithmetic number, because the mean of its divisors is an integer number (40574942100).

Almost surely, 2^645261135521 is an apocalyptic number.

It is an amenable number.

645261135521 is a deficient number, since it is larger than the sum of its proper divisors (3937938079).

645261135521 is a wasteful number, since it uses less digits than its factorization.

645261135521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4784.

The product of its digits is 216000, while the sum is 41.

The spelling of 645261135521 in words is "six hundred forty-five billion, two hundred sixty-one million, one hundred thirty-five thousand, five hundred twenty-one".