816505920 has 420 divisors, whose sum is σ = 3113661540. Its totient is φ = 203046912.

The previous prime is 816505909. The next prime is 816505961. The reversal of 816505920 is 29505618.

816505920 = T₃₈₁₆ + T₃₈₁₇ + ... + T₃₉₂₄.

It is a happy number.

816505920 is a `hidden beast` number, since 8 + 1 + 65 + 0 + 592 + 0 = 666.

It can be written as a sum of positive squares in 6 ways, for example, as 83612736 + 732893184 = 9144^2 + 27072^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 7490826 + ... + 7490934.

Almost surely, 2^816505920 is an apocalyptic number.

816505920 is a gapful number since it is divisible by the number (80) 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 816505920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1556830770).

816505920 is an abundant number, since it is smaller than the sum of its proper divisors (2297155620).

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

816505920 is a wasteful number, since it uses less digits than its factorization.

816505920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172 (or 136 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 816505920 is about 28574.5677132656. The cubic root of 816505920 is about 934.6588286935.

The spelling of 816505920 in words is "eight hundred sixteen million, five hundred five thousand, nine hundred twenty".