21385579 has 4 divisors (see below), whose sum is σ = 21450520. Its totient is φ = 21320640.

The previous prime is 21385549. The next prime is 21385591. The reversal of 21385579 is 97558312.

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 21385579 - 2¹³ = 21377387 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21385549) 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, 31974 + ... + 32635.

It is an arithmetic number, because the mean of its divisors is an integer number (5362630).

Almost surely, 2^21385579 is an apocalyptic number.

21385579 is a deficient number, since it is larger than the sum of its proper divisors (64941).

21385579 is an equidigital number, since it uses as much as digits as its factorization.

21385579 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64940.

The product of its digits is 75600, while the sum is 40.

The square root of 21385579 is about 4624.4544543113. The cubic root of 21385579 is about 277.5707321792.

The spelling of 21385579 in words is "twenty-one million, three hundred eighty-five thousand, five hundred seventy-nine".