21579847 has 4 divisors (see below), whose sum is σ = 21704760. Its totient is φ = 21454936.

The previous prime is 21579827. The next prime is 21579853. The reversal of 21579847 is 74897512.

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 21579847 - 2¹⁵ = 21547079 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 (21579827) 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, 62197 + ... + 62542.

It is an arithmetic number, because the mean of its divisors is an integer number (5426190).

Almost surely, 2^21579847 is an apocalyptic number.

21579847 is a deficient number, since it is larger than the sum of its proper divisors (124913).

21579847 is a wasteful number, since it uses less digits than its factorization.

21579847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124912.

The product of its digits is 141120, while the sum is 43.

The square root of 21579847 is about 4645.4113919006. The cubic root of 21579847 is about 278.4086901587.

The spelling of 21579847 in words is "twenty-one million, five hundred seventy-nine thousand, eight hundred forty-seven".