1645891440 has 40 divisors (see below), whose sum is σ = 5102264208. Its totient is φ = 438904320.

The previous prime is 1645891439. The next prime is 1645891453. The reversal of 1645891440 is 441985461.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 1645891392 and 1645891401.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3428701 + ... + 3429180.

Almost surely, 2^1645891440 is an apocalyptic number.

1645891440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1645891440 is an abundant number, since it is smaller than the sum of its proper divisors (3456372768).

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

1645891440 is a wasteful number, since it uses less digits than its factorization.

1645891440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6857897 (or 6857891 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 42.

The square root of 1645891440 is about 40569.5876242291. The cubic root of 1645891440 is about 1180.6841383701.

The spelling of 1645891440 in words is "one billion, six hundred forty-five million, eight hundred ninety-one thousand, four hundred forty".