21690447 has 8 divisors (see below), whose sum is σ = 29593344. Its totient is φ = 14123928.

The previous prime is 21690413. The next prime is 21690451. The reversal of 21690447 is 74409612.

It is a happy number.

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

It is not a de Polignac number, because 21690447 - 2²⁰ = 20641871 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690407) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 83943 + ... + 84200.

It is an arithmetic number, because the mean of its divisors is an integer number (3699168).

Almost surely, 2^21690447 is an apocalyptic number.

21690447 is a deficient number, since it is larger than the sum of its proper divisors (7902897).

21690447 is a wasteful number, since it uses less digits than its factorization.

21690447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168189.

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 21690447 is about 4657.3003982994. The cubic root of 21690447 is about 278.8835088764.

The spelling of 21690447 in words is "twenty-one million, six hundred ninety thousand, four hundred forty-seven".