645555391 has 8 divisors (see below), whose sum is σ = 714003584. Its totient is φ = 579791520.

The previous prime is 645555349. The next prime is 645555401. The reversal of 645555391 is 193555546.

645555391 = 4159² + 4160² + ... + 4195².

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

It is a cyclic number.

It is not a de Polignac number, because 645555391 - 2¹¹ = 645553343 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 (645555091) 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, 670575 + ... + 671536.

It is an arithmetic number, because the mean of its divisors is an integer number (89250448).

Almost surely, 2^645555391 is an apocalyptic number.

645555391 is a deficient number, since it is larger than the sum of its proper divisors (68448193).

645555391 is a wasteful number, since it uses less digits than its factorization.

645555391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1342161.

The product of its digits is 405000, while the sum is 43.

The square root of 645555391 is about 25407.7820952558. The cubic root of 645555391 is about 864.2601806840.

The spelling of 645555391 in words is "six hundred forty-five million, five hundred fifty-five thousand, three hundred ninety-one".