21289887 has 12 divisors (see below), whose sum is σ = 30793464. Its totient is φ = 14174160.

The previous prime is 21289883. The next prime is 21289889. The reversal of 21289887 is 78898212.

It is a happy number.

It is not a de Polignac number, because 21289887 - 2² = 21289883 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21289883) 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, 9628 + ... + 11630.

It is an arithmetic number, because the mean of its divisors is an integer number (2566122).

Almost surely, 2^21289887 is an apocalyptic number.

21289887 is a deficient number, since it is larger than the sum of its proper divisors (9503577).

21289887 is a wasteful number, since it uses less digits than its factorization.

21289887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3190 (or 3187 counting only the distinct ones).

The product of its digits is 129024, while the sum is 45.

The square root of 21289887 is about 4614.0965529560. The cubic root of 21289887 is about 277.1561067536.

The spelling of 21289887 in words is "twenty-one million, two hundred eighty-nine thousand, eight hundred eighty-seven".