813661920 has 288 divisors, whose sum is σ = 2888252640. Its totient is φ = 208465920.

The previous prime is 813661913. The next prime is 813661943. The reversal of 813661920 is 29166318.

813661920 is a `hidden beast` number, since 8 + 1 + 36 + 619 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (288).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 5182482 + ... + 5182638.

It is an arithmetic number, because the mean of its divisors is an integer number (10028655).

Almost surely, 2^813661920 is an apocalyptic number.

813661920 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 813661920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1444126320).

813661920 is an abundant number, since it is smaller than the sum of its proper divisors (2074590720).

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

813661920 is a wasteful number, since it uses less digits than its factorization.

813661920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298 (or 287 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 813661920 is about 28524.7597711181. The cubic root of 813661920 is about 933.5723854790.

The spelling of 813661920 in words is "eight hundred thirteen million, six hundred sixty-one thousand, nine hundred twenty".