1645403220 has 120 divisors (see below), whose sum is σ = 5172418944. Its totient is φ = 437863104.

The previous prime is 1645403197. The next prime is 1645403239. The reversal of 1645403220 is 223045461.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1202977 + ... + 1204343.

Almost surely, 2^1645403220 is an apocalyptic number.

1645403220 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 1645403220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2586209472).

1645403220 is an abundant number, since it is smaller than the sum of its proper divisors (3527015724).

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

1645403220 is a wasteful number, since it uses less digits than its factorization.

1645403220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2131 (or 2120 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 1645403220 is about 40563.5701091509. The cubic root of 1645403220 is about 1180.5673848991.

Adding to 1645403220 its reverse (223045461), we get a palindrome (1868448681).

The spelling of 1645403220 in words is "one billion, six hundred forty-five million, four hundred three thousand, two hundred twenty".