21407689 has 4 divisors (see below), whose sum is σ = 21502224. Its totient is φ = 21313156.

The previous prime is 21407681. The next prime is 21407693. The reversal of 21407689 is 98670412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21407689 - 2³ = 21407681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21407681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46927 + ... + 47380.

It is an arithmetic number, because the mean of its divisors is an integer number (5375556).

Almost surely, 2^21407689 is an apocalyptic number.

It is an amenable number.

21407689 is a deficient number, since it is larger than the sum of its proper divisors (94535).

21407689 is an equidigital number, since it uses as much as digits as its factorization.

21407689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94534.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21407689 is about 4626.8443889978. The cubic root of 21407689 is about 277.6663569786. Note that the first 3 decimals are identical.

The spelling of 21407689 in words is "twenty-one million, four hundred seven thousand, six hundred eighty-nine".