21323987 has 4 divisors (see below), whose sum is σ = 21531120. Its totient is φ = 21116856.

The previous prime is 21323983. The next prime is 21323989. The reversal of 21323987 is 78932312.

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 21323987 - 2² = 21323983 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21323983) 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, 103412 + ... + 103617.

It is an arithmetic number, because the mean of its divisors is an integer number (5382780).

Almost surely, 2^21323987 is an apocalyptic number.

21323987 is a deficient number, since it is larger than the sum of its proper divisors (207133).

21323987 is a wasteful number, since it uses less digits than its factorization.

21323987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207132.

The product of its digits is 18144, while the sum is 35.

The square root of 21323987 is about 4617.7902724139. The cubic root of 21323987 is about 277.3040014140.

The spelling of 21323987 in words is "twenty-one million, three hundred twenty-three thousand, nine hundred eighty-seven".