21689487 has 12 divisors (see below), whose sum is σ = 31372744. Its totient is φ = 14439600.

The previous prime is 21689471. The next prime is 21689497. The reversal of 21689487 is 78498612.

21689487 is a `hidden beast` number, since 2 + 168 + 9 + 487 = 666.

It is not a de Polignac number, because 21689487 - 2⁴ = 21689471 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 (21689407) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8313 + ... + 10605.

Almost surely, 2^21689487 is an apocalyptic number.

21689487 is a deficient number, since it is larger than the sum of its proper divisors (9683257).

21689487 is a wasteful number, since it uses less digits than its factorization.

21689487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3350 (or 3347 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The square root of 21689487 is about 4657.1973331608. The cubic root of 21689487 is about 278.8793944365.

The spelling of 21689487 in words is "twenty-one million, six hundred eighty-nine thousand, four hundred eighty-seven".