21813806 has 8 divisors (see below), whose sum is σ = 37395120. Its totient is φ = 9348768.

The previous prime is 21813761. The next prime is 21813809. The reversal of 21813806 is 60831812.

21813806 = T₂₄₉₃ + T₂₄₉₄ + ... + T₂₄₉₉.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21813809) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 779051 + ... + 779078.

It is an arithmetic number, because the mean of its divisors is an integer number (4674390).

Almost surely, 2^21813806 is an apocalyptic number.

21813806 is a deficient number, since it is larger than the sum of its proper divisors (15581314).

21813806 is a wasteful number, since it uses less digits than its factorization.

21813806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1558138.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21813806 is about 4670.5252381290. The cubic root of 21813806 is about 279.4112031952.

The spelling of 21813806 in words is "twenty-one million, eight hundred thirteen thousand, eight hundred six".