21694221 has 12 divisors (see below), whose sum is σ = 32698848. Its totient is φ = 13833864.

The previous prime is 21694217. The next prime is 21694237. The reversal of 21694221 is 12249612.

It is not a de Polignac number, because 21694221 - 2² = 21694217 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21694201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 52195 + ... + 52608.

It is an arithmetic number, because the mean of its divisors is an integer number (2724904).

Almost surely, 2^21694221 is an apocalyptic number.

It is an amenable number.

21694221 is a deficient number, since it is larger than the sum of its proper divisors (11004627).

21694221 is a wasteful number, since it uses less digits than its factorization.

21694221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104832 (or 104829 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21694221 is about 4657.7055510197. The cubic root of 21694221 is about 278.8996825914.

The spelling of 21694221 in words is "twenty-one million, six hundred ninety-four thousand, two hundred twenty-one".