21806434 has 16 divisors (see below), whose sum is σ = 36441720. Its totient is φ = 9717120.

The previous prime is 21806429. The next prime is 21806437. The reversal of 21806434 is 43460812.

It can be written as a sum of positive squares in 4 ways, for example, as 17665209 + 4141225 = 4203^2 + 2035^2 .

It is not an unprimeable number, because it can be changed into a prime (21806437) 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 7 ways as a sum of consecutive naturals, for example, 13707 + ... + 15214.

Almost surely, 2^21806434 is an apocalyptic number.

21806434 is a deficient number, since it is larger than the sum of its proper divisors (14635286).

21806434 is a wasteful number, since it uses less digits than its factorization.

21806434 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28965.

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 21806434 is about 4669.7359668401. The cubic root of 21806434 is about 279.3797238732.

The spelling of 21806434 in words is "twenty-one million, eight hundred six thousand, four hundred thirty-four".