21288887 has 4 divisors (see below), whose sum is σ = 21313776. Its totient is φ = 21264000.

The previous prime is 21288863. The next prime is 21288893. The reversal of 21288887 is 78888212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21288887 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 (21288857) 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, 11114 + ... + 12887.

It is an arithmetic number, because the mean of its divisors is an integer number (5328444).

Almost surely, 2^21288887 is an apocalyptic number.

21288887 is a deficient number, since it is larger than the sum of its proper divisors (24889).

21288887 is an equidigital number, since it uses as much as digits as its factorization.

21288887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24888.

The product of its digits is 114688, while the sum is 44.

The square root of 21288887 is about 4613.9881881080. The cubic root of 21288887 is about 277.1517672841.

The spelling of 21288887 in words is "twenty-one million, two hundred eighty-eight thousand, eight hundred eighty-seven".