21417887 has 4 divisors (see below), whose sum is σ = 21537720. Its totient is φ = 21298056.

The previous prime is 21417871. The next prime is 21417889. The reversal of 21417887 is 78871412.

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

It is a cyclic number.

It is not a de Polignac number, because 21417887 - 2⁴ = 21417871 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21417887.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21417889) 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, 59648 + ... + 60005.

It is an arithmetic number, because the mean of its divisors is an integer number (5384430).

Almost surely, 2^21417887 is an apocalyptic number.

21417887 is a deficient number, since it is larger than the sum of its proper divisors (119833).

21417887 is a wasteful number, since it uses less digits than its factorization.

21417887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119832.

The product of its digits is 25088, while the sum is 38.

The square root of 21417887 is about 4627.9463047879. The cubic root of 21417887 is about 277.7104407031.

The spelling of 21417887 in words is "twenty-one million, four hundred seventeen thousand, eight hundred eighty-seven".