21821766 has 32 divisors (see below), whose sum is σ = 46642560. Its totient is φ = 6785856.

The previous prime is 21821759. The next prime is 21821797. The reversal of 21821766 is 66712812.

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 15 ways as a sum of consecutive naturals, for example, 6210 + ... + 9066.

It is an arithmetic number, because the mean of its divisors is an integer number (1457580).

Almost surely, 2^21821766 is an apocalyptic number.

21821766 is an abundant number, since it is smaller than the sum of its proper divisors (24820794).

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

21821766 is a wasteful number, since it uses less digits than its factorization.

21821766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2948.

The product of its digits is 8064, while the sum is 33.

The square root of 21821766 is about 4671.3773129560. The cubic root of 21821766 is about 279.4451853852.

The spelling of 21821766 in words is "twenty-one million, eight hundred twenty-one thousand, seven hundred sixty-six".