645444821 has 8 divisors (see below), whose sum is σ = 745940160. Its totient is φ = 547021728.

The previous prime is 645444809. The next prime is 645444829. The reversal of 645444821 is 128444546.

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 645444821 - 2²⁶ = 578335957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645444829) 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, 517391 + ... + 518636.

It is an arithmetic number, because the mean of its divisors is an integer number (93242520).

Almost surely, 2^645444821 is an apocalyptic number.

It is an amenable number.

645444821 is a deficient number, since it is larger than the sum of its proper divisors (100495339).

645444821 is a wasteful number, since it uses less digits than its factorization.

645444821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1036123.

The product of its digits is 122880, while the sum is 38.

The square root of 645444821 is about 25405.6060939313. The cubic root of 645444821 is about 864.2108346966.

The spelling of 645444821 in words is "six hundred forty-five million, four hundred forty-four thousand, eight hundred twenty-one".