21679845 has 64 divisors (see below), whose sum is σ = 41057280. Its totient is φ = 9651200.

The previous prime is 21679843. The next prime is 21679871. The reversal of 21679845 is 54897612.

It is not a de Polignac number, because 21679845 - 2¹ = 21679843 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21679797 and 21679806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21679843) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 165430 + ... + 165560.

It is an arithmetic number, because the mean of its divisors is an integer number (641520).

Almost surely, 2^21679845 is an apocalyptic number.

It is an amenable number.

21679845 is a deficient number, since it is larger than the sum of its proper divisors (19377435).

21679845 is a wasteful number, since it uses less digits than its factorization.

21679845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226.

The product of its digits is 120960, while the sum is 42.

The square root of 21679845 is about 4656.1620461492. The cubic root of 21679845 is about 278.8380632965.

The spelling of 21679845 in words is "twenty-one million, six hundred seventy-nine thousand, eight hundred forty-five".