21805794 has 64 divisors (see below), whose sum is σ = 51367680. Its totient is φ = 6842880.

The previous prime is 21805783. The next prime is 21805807. The reversal of 21805794 is 49750812.

21805794 = T₁₂₂ + T₁₂₃ + ... + T₅₀₉.

21805794 is a `hidden beast` number, since 2 + 1 + 80 + 579 + 4 = 666.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

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 31 ways as a sum of consecutive naturals, for example, 120384 + ... + 120564.

It is an arithmetic number, because the mean of its divisors is an integer number (802620).

Almost surely, 2^21805794 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21805794, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25683840).

21805794 is an abundant number, since it is smaller than the sum of its proper divisors (29561886).

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

21805794 is a wasteful number, since it uses less digits than its factorization.

21805794 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312 (or 306 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21805794 is about 4669.6674399790. The cubic root of 21805794 is about 279.3769906619.

It can be divided in two parts, 21 and 805794, that added together give a triangular number (805815 = T₁₂₆₉).

The spelling of 21805794 in words is "twenty-one million, eight hundred five thousand, seven hundred ninety-four".