645606621 has 48 divisors (see below), whose sum is σ = 1051719552. Its totient is φ = 378268800.

The previous prime is 645606607. The next prime is 645606679. The reversal of 645606621 is 126606546.

It is a happy number.

645606621 is a `hidden beast` number, since 6 + 45 + 606 + 6 + 2 + 1 = 666.

It is not a de Polignac number, because 645606621 - 2⁶ = 645606557 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645606721) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 371671 + ... + 373403.

It is an arithmetic number, because the mean of its divisors is an integer number (21910824).

Almost surely, 2^645606621 is an apocalyptic number.

It is an amenable number.

645606621 is a deficient number, since it is larger than the sum of its proper divisors (406112931).

645606621 is a wasteful number, since it uses less digits than its factorization.

645606621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1874 (or 1871 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The square root of 645606621 is about 25408.7902309417. The cubic root of 645606621 is about 864.2830420725.

The spelling of 645606621 in words is "six hundred forty-five million, six hundred six thousand, six hundred twenty-one".