21869987 has 4 divisors (see below), whose sum is σ = 22820880. Its totient is φ = 20919096.

The previous prime is 21869983. The next prime is 21869989. The reversal of 21869987 is 78996812.

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 21869987 - 2² = 21869983 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21869983) 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, 475412 + ... + 475457.

It is an arithmetic number, because the mean of its divisors is an integer number (5705220).

Almost surely, 2^21869987 is an apocalyptic number.

21869987 is a deficient number, since it is larger than the sum of its proper divisors (950893).

21869987 is an equidigital number, since it uses as much as digits as its factorization.

21869987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 950892.

The product of its digits is 435456, while the sum is 50.

The square root of 21869987 is about 4676.5357905184. The cubic root of 21869987 is about 279.6508701257.

The spelling of 21869987 in words is "twenty-one million, eight hundred sixty-nine thousand, nine hundred eighty-seven".