21506689 has 8 divisors (see below), whose sum is σ = 22682240. Its totient is φ = 20335536.

The previous prime is 21506669. The next prime is 21506707. The reversal of 21506689 is 98660512.

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

It is a cyclic number.

It is not a de Polignac number, because 21506689 - 2¹⁷ = 21375617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21506609) 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, 15544 + ... + 16870.

It is an arithmetic number, because the mean of its divisors is an integer number (2835280).

Almost surely, 2^21506689 is an apocalyptic number.

It is an amenable number.

21506689 is a deficient number, since it is larger than the sum of its proper divisors (1175551).

21506689 is a wasteful number, since it uses less digits than its factorization.

21506689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2199.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 21506689 is about 4637.5304850750. The cubic root of 21506689 is about 278.0937221738.

The spelling of 21506689 in words is "twenty-one million, five hundred six thousand, six hundred eighty-nine".