21379287 has 4 divisors (see below), whose sum is σ = 28505720. Its totient is φ = 14252856.

The previous prime is 21379283. The next prime is 21379289. The reversal of 21379287 is 78297312.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21379287 - 2² = 21379283 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21379283) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3563212 + ... + 3563217.

It is an arithmetic number, because the mean of its divisors is an integer number (7126430).

Almost surely, 2^21379287 is an apocalyptic number.

21379287 is a deficient number, since it is larger than the sum of its proper divisors (7126433).

21379287 is an equidigital number, since it uses as much as digits as its factorization.

21379287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7126432.

The product of its digits is 42336, while the sum is 39.

The square root of 21379287 is about 4623.7741078041. The cubic root of 21379287 is about 277.5435075035.

The spelling of 21379287 in words is "twenty-one million, three hundred seventy-nine thousand, two hundred eighty-seven".