1605811920 has 80 divisors (see below), whose sum is σ = 4998852672. Its totient is φ = 426424320.

The previous prime is 1605811859. The next prime is 1605811931. The reversal of 1605811920 is 291185061.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43959 + ... + 71721.

Almost surely, 2^1605811920 is an apocalyptic number.

1605811920 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 1605811920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2499426336).

1605811920 is an abundant number, since it is smaller than the sum of its proper divisors (3393040752).

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

1605811920 is a wasteful number, since it uses less digits than its factorization.

1605811920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28020 (or 28014 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 33.

The square root of 1605811920 is about 40072.5831460863. The cubic root of 1605811920 is about 1171.0215637675.

Adding to 1605811920 its reverse (291185061), we get a palindrome (1896996981).

The spelling of 1605811920 in words is "one billion, six hundred five million, eight hundred eleven thousand, nine hundred twenty".