645701940 has 72 divisors (see below), whose sum is σ = 2109300648. Its totient is φ = 158941440.

The previous prime is 645701923. The next prime is 645701957. The reversal of 645701940 is 49107546.

645701940 is a `hidden beast` number, since 645 + 7 + 0 + 1 + 9 + 4 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (645701923) and next prime (645701957).

It can be written as a sum of positive squares in 4 ways, for example, as 338724 + 645363216 = 582^2 + 25404^2 .

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 = 645701895 and 645701904.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 135631 + ... + 140310.

Almost surely, 2^645701940 is an apocalyptic number.

645701940 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645701940 is an abundant number, since it is smaller than the sum of its proper divisors (1463598708).

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

645701940 is a wasteful number, since it uses less digits than its factorization.

645701940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275969 (or 275964 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The square root of 645701940 is about 25410.6658708504. The cubic root of 645701940 is about 864.3255749600.

The spelling of 645701940 in words is "six hundred forty-five million, seven hundred one thousand, nine hundred forty".