21087923 has 8 divisors (see below), whose sum is σ = 21494880. Its totient is φ = 20684160.

The previous prime is 21087919. The next prime is 21087943. The reversal of 21087923 is 32978012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21087923 - 2² = 21087919 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 21087923.

It is not an unprimeable number, because it can be changed into a prime (21087943) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15611 + ... + 16907.

It is an arithmetic number, because the mean of its divisors is an integer number (2686860).

Almost surely, 2^21087923 is an apocalyptic number.

21087923 is a deficient number, since it is larger than the sum of its proper divisors (406957).

21087923 is a wasteful number, since it uses less digits than its factorization.

21087923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1597.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 21087923 is about 4592.1588604925. The cubic root of 21087923 is about 276.2769178605.

The spelling of 21087923 in words is "twenty-one million, eighty-seven thousand, nine hundred twenty-three".