645837840 has 80 divisors (see below), whose sum is σ = 2224560000. Its totient is φ = 172222848.

The previous prime is 645837833. The next prime is 645837851. The reversal of 645837840 is 48738546.

645837840 is a `hidden beast` number, since 64 + 583 + 7 + 8 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 147340 + ... + 151659.

It is an arithmetic number, because the mean of its divisors is an integer number (27807000).

Almost surely, 2^645837840 is an apocalyptic number.

645837840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645837840 is an abundant number, since it is smaller than the sum of its proper divisors (1578722160).

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

645837840 is a wasteful number, since it uses less digits than its factorization.

645837840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 299021 (or 299009 counting only the distinct ones).

The product of its (nonzero) digits is 645120, while the sum is 45.

The square root of 645837840 is about 25413.3398041265. The cubic root of 645837840 is about 864.3862085117.

The spelling of 645837840 in words is "six hundred forty-five million, eight hundred thirty-seven thousand, eight hundred forty".