21087679 has 4 divisors (see below), whose sum is σ = 21151720. Its totient is φ = 21023640.

The previous prime is 21087643. The next prime is 21087683. The reversal of 21087679 is 97678012.

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 21087679 - 2¹⁹ = 20563391 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 (21087779) 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, 31524 + ... + 32185.

It is an arithmetic number, because the mean of its divisors is an integer number (5287930).

Almost surely, 2^21087679 is an apocalyptic number.

21087679 is a deficient number, since it is larger than the sum of its proper divisors (64041).

21087679 is an equidigital number, since it uses as much as digits as its factorization.

21087679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64040.

The product of its (nonzero) digits is 42336, while the sum is 40.

The square root of 21087679 is about 4592.1322933905. The cubic root of 21087679 is about 276.2758522928.

The spelling of 21087679 in words is "twenty-one million, eighty-seven thousand, six hundred seventy-nine".