1645756640 has 72 divisors (see below), whose sum is σ = 4245954552. Its totient is φ = 597838080.

The previous prime is 1645756601. The next prime is 1645756643. The reversal of 1645756640 is 466575461.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a junction number, because it is equal to n+sod(n) for n = 1645756591 and 1645756600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645756643) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1701437 + ... + 1702403.

It is an arithmetic number, because the mean of its divisors is an integer number (58971591).

Almost surely, 2^1645756640 is an apocalyptic number.

1645756640 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 1645756640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2122977276).

1645756640 is an abundant number, since it is smaller than the sum of its proper divisors (2600197912).

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

1645756640 is an frugal number, since it uses more digits than its factorization.

1645756640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1960 (or 985 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 44.

The square root of 1645756640 is about 40567.9262472215. The cubic root of 1645756640 is about 1180.6519044565.

The spelling of 1645756640 in words is "one billion, six hundred forty-five million, seven hundred fifty-six thousand, six hundred forty".