645644553 has 8 divisors (see below), whose sum is σ = 860985216. Its totient is φ = 430366800.

The previous prime is 645644551. The next prime is 645644563. The reversal of 645644553 is 355446546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 645644553 - 2¹ = 645644551 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645644551) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19488 + ... + 40878.

It is an arithmetic number, because the mean of its divisors is an integer number (107623152).

Almost surely, 2^645644553 is an apocalyptic number.

It is an amenable number.

645644553 is a deficient number, since it is larger than the sum of its proper divisors (215340663).

645644553 is a wasteful number, since it uses less digits than its factorization.

645644553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31455.

The product of its digits is 864000, while the sum is 42.

The square root of 645644553 is about 25409.5366545713. The cubic root of 645644553 is about 864.2999684491.

The spelling of 645644553 in words is "six hundred forty-five million, six hundred forty-four thousand, five hundred fifty-three".