645047640 has 192 divisors, whose sum is σ = 2183875200. Its totient is φ = 164975616.

The previous prime is 645047639. The next prime is 645047651. The reversal of 645047640 is 46740546.

645047640 is a `hidden beast` number, since 6 + 4 + 5 + 0 + 4 + 7 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 645047595 and 645047604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1051974 + ... + 1052586.

It is an arithmetic number, because the mean of its divisors is an integer number (11374350).

Almost surely, 2^645047640 is an apocalyptic number.

645047640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645047640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1091937600).

645047640 is an abundant number, since it is smaller than the sum of its proper divisors (1538827560).

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

645047640 is a wasteful number, since it uses less digits than its factorization.

645047640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 746 (or 739 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 36.

The square root of 645047640 is about 25397.7880926667. The cubic root of 645047640 is about 864.0335313633.

The spelling of 645047640 in words is "six hundred forty-five million, forty-seven thousand, six hundred forty".