1645539840 has 640 divisors, whose sum is σ = 7070976000. Its totient is φ = 354336768.

The previous prime is 1645539817. The next prime is 1645539869. The reversal of 1645539840 is 489355461.

1645539840 is a `hidden beast` number, since 1 + 6 + 4 + 553 + 98 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

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 63 ways as a sum of consecutive naturals, for example, 9192871 + ... + 9193049.

It is an arithmetic number, because the mean of its divisors is an integer number (11048400).

Almost surely, 2^1645539840 is an apocalyptic number.

1645539840 is a gapful number since it is divisible by the number (10) 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 1645539840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3535488000).

1645539840 is an abundant number, since it is smaller than the sum of its proper divisors (5425436160).

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

1645539840 is a wasteful number, since it uses less digits than its factorization.

1645539840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 237 (or 215 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 45.

The square root of 1645539840 is about 40565.2540975648. The cubic root of 1645539840 is about 1180.6000586840.

The spelling of 1645539840 in words is "one billion, six hundred forty-five million, five hundred thirty-nine thousand, eight hundred forty".