645757820 has 24 divisors (see below), whose sum is σ = 1356569424. Its totient is φ = 258212096.

The previous prime is 645757817. The next prime is 645757829. The reversal of 645757820 is 28757546.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645757829) 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, 104867 + ... + 110853.

It is an arithmetic number, because the mean of its divisors is an integer number (56523726).

Almost surely, 2^645757820 is an apocalyptic number.

It is an amenable number.

645757820 is an abundant number, since it is smaller than the sum of its proper divisors (710811604).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645757820 is a wasteful number, since it uses less digits than its factorization.

645757820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11389 (or 11387 counting only the distinct ones).

The product of its (nonzero) digits is 470400, while the sum is 44.

The square root of 645757820 is about 25411.7653853486. The cubic root of 645757820 is about 864.3505075782.

The spelling of 645757820 in words is "six hundred forty-five million, seven hundred fifty-seven thousand, eight hundred twenty".