21889987 has 4 divisors (see below), whose sum is σ = 25017136. Its totient is φ = 18762840.

The previous prime is 21889981. The next prime is 21889991. The reversal of 21889987 is 78998812.

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 21889987 - 2¹¹ = 21887939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21889981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1563564 + ... + 1563577.

It is an arithmetic number, because the mean of its divisors is an integer number (6254284).

Almost surely, 2^21889987 is an apocalyptic number.

21889987 is a deficient number, since it is larger than the sum of its proper divisors (3127149).

21889987 is an equidigital number, since it uses as much as digits as its factorization.

21889987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3127148.

The product of its digits is 580608, while the sum is 52.

The square root of 21889987 is about 4678.6736368334. The cubic root of 21889987 is about 279.7360906204.

The spelling of 21889987 in words is "twenty-one million, eight hundred eighty-nine thousand, nine hundred eighty-seven".