21689207 has 4 divisors (see below), whose sum is σ = 22632240. Its totient is φ = 20746176.

The previous prime is 21689197. The next prime is 21689233. The reversal of 21689207 is 70298612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21689207 - 2⁸ = 21688951 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21689237) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 471482 + ... + 471527.

It is an arithmetic number, because the mean of its divisors is an integer number (5658060).

Almost surely, 2^21689207 is an apocalyptic number.

21689207 is a deficient number, since it is larger than the sum of its proper divisors (943033).

21689207 is an equidigital number, since it uses as much as digits as its factorization.

21689207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 943032.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21689207 is about 4657.1672720657. The cubic root of 21689207 is about 278.8781943687.

The spelling of 21689207 in words is "twenty-one million, six hundred eighty-nine thousand, two hundred seven".