21210689 has 4 divisors (see below), whose sum is σ = 21301956. Its totient is φ = 21119424.

The previous prime is 21210649. The next prime is 21210691. The reversal of 21210689 is 98601212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10452289 + 10758400 = 3233^2 + 3280^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210689 - 2⁸ = 21210433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21210619) 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, 45284 + ... + 45749.

It is an arithmetic number, because the mean of its divisors is an integer number (5325489).

Almost surely, 2^21210689 is an apocalyptic number.

It is an amenable number.

21210689 is a deficient number, since it is larger than the sum of its proper divisors (91267).

21210689 is an equidigital number, since it uses as much as digits as its factorization.

21210689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91266.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21210689 is about 4605.5063782390. The cubic root of 21210689 is about 276.8120077946.

It can be divided in two parts, 212 and 10689, that added together give a palindrome (10901).

The spelling of 21210689 in words is "twenty-one million, two hundred ten thousand, six hundred eighty-nine".