1645666380 has 144 divisors (see below), whose sum is σ = 5321971200. Its totient is φ = 410417280.

The previous prime is 1645666367. The next prime is 1645666387. The reversal of 1645666380 is 836665461.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (1645666387) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 267135 + ... + 273225.

Almost surely, 2^1645666380 is an apocalyptic number.

1645666380 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 1645666380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2660985600).

1645666380 is an abundant number, since it is smaller than the sum of its proper divisors (3676304820).

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

1645666380 is a wasteful number, since it uses less digits than its factorization.

1645666380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6204 (or 6199 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 45.

The square root of 1645666380 is about 40566.8137767806. The cubic root of 1645666380 is about 1180.6303201415.

The spelling of 1645666380 in words is "one billion, six hundred forty-five million, six hundred sixty-six thousand, three hundred eighty".