645441621 has 16 divisors (see below), whose sum is σ = 942731328. Its totient is φ = 389548800.

The previous prime is 645441593. The next prime is 645441631. The reversal of 645441621 is 126144546.

It is not a de Polignac number, because 645441621 - 2¹⁰ = 645440597 is a prime.

It is a super-2 number, since 2×645441621² = 833189772238215282, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645441631) 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, 32626 + ... + 48531.

It is an arithmetic number, because the mean of its divisors is an integer number (58920708).

Almost surely, 2^645441621 is an apocalyptic number.

It is an amenable number.

645441621 is a deficient number, since it is larger than the sum of its proper divisors (297289707).

645441621 is a wasteful number, since it uses less digits than its factorization.

645441621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81412.

The product of its digits is 23040, while the sum is 33.

The square root of 645441621 is about 25405.5431156273. The cubic root of 645441621 is about 864.2094064933.

The spelling of 645441621 in words is "six hundred forty-five million, four hundred forty-one thousand, six hundred twenty-one".