645474021 has 4 divisors (see below), whose sum is σ = 860632032. Its totient is φ = 430316012.

The previous prime is 645474017. The next prime is 645474043. The reversal of 645474021 is 120474546.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 645474021 - 2² = 645474017 is a prime.

It is a super-3 number, since 3×645474021³ (a number of 27 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645474421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107579001 + ... + 107579006.

It is an arithmetic number, because the mean of its divisors is an integer number (215158008).

Almost surely, 2^645474021 is an apocalyptic number.

It is an amenable number.

645474021 is a deficient number, since it is larger than the sum of its proper divisors (215158011).

645474021 is a wasteful number, since it uses less digits than its factorization.

645474021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215158010.

The product of its (nonzero) digits is 26880, while the sum is 33.

The square root of 645474021 is about 25406.1807637433. The cubic root of 645474021 is about 864.2238668335.

The spelling of 645474021 in words is "six hundred forty-five million, four hundred seventy-four thousand, twenty-one".