21593987 has 4 divisors (see below), whose sum is σ = 22532880. Its totient is φ = 20655096.

The previous prime is 21593983. The next prime is 21594019. The reversal of 21593987 is 78939512.

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 21593987 - 2² = 21593983 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21593983) 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, 469412 + ... + 469457.

It is an arithmetic number, because the mean of its divisors is an integer number (5633220).

Almost surely, 2^21593987 is an apocalyptic number.

21593987 is a deficient number, since it is larger than the sum of its proper divisors (938893).

21593987 is an equidigital number, since it uses as much as digits as its factorization.

21593987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 938892.

The product of its digits is 136080, while the sum is 44.

The square root of 21593987 is about 4646.9330746203. The cubic root of 21593987 is about 278.4694851428.

The spelling of 21593987 in words is "twenty-one million, five hundred ninety-three thousand, nine hundred eighty-seven".