21809814 has 16 divisors (see below), whose sum is σ = 46975152. Its totient is φ = 6710688.

The previous prime is 21809789. The next prime is 21809863. The reversal of 21809814 is 41890812.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 139729 + ... + 139884.

It is an arithmetic number, because the mean of its divisors is an integer number (2935947).

Almost surely, 2^21809814 is an apocalyptic number.

21809814 is an abundant number, since it is smaller than the sum of its proper divisors (25165338).

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

21809814 is a wasteful number, since it uses less digits than its factorization.

21809814 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279631.

The product of its (nonzero) digits is 4608, while the sum is 33.

The square root of 21809814 is about 4670.0978576471. The cubic root of 21809814 is about 279.3941577582.

The spelling of 21809814 in words is "twenty-one million, eight hundred nine thousand, eight hundred fourteen".