645471281 has 8 divisors (see below), whose sum is σ = 794426304. Its totient is φ = 510702480.

The previous prime is 645471263. The next prime is 645471293. The reversal of 645471281 is 182174546.

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 645471281 - 2²⁶ = 578362417 is a prime.

It is a super-2 number, since 2×645471281² = 833266349191561922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645471221) 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, 3546455 + ... + 3546636.

It is an arithmetic number, because the mean of its divisors is an integer number (99303288).

Almost surely, 2^645471281 is an apocalyptic number.

It is an amenable number.

645471281 is a deficient number, since it is larger than the sum of its proper divisors (148955023).

645471281 is a wasteful number, since it uses less digits than its factorization.

645471281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7093111.

The product of its digits is 53760, while the sum is 38.

The square root of 645471281 is about 25406.1268397999. The cubic root of 645471281 is about 864.2226439716. Note that the first 3 decimals are identical.

The spelling of 645471281 in words is "six hundred forty-five million, four hundred seventy-one thousand, two hundred eighty-one".