21605859 has 48 divisors (see below), whose sum is σ = 36167040. Its totient is φ = 12778560.

The previous prime is 21605849. The next prime is 21605863. The reversal of 21605859 is 95850612.

It is a happy number.

It is not a de Polignac number, because 21605859 - 2¹² = 21601763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21605849) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 157639 + ... + 157775.

It is an arithmetic number, because the mean of its divisors is an integer number (753480).

Almost surely, 2^21605859 is an apocalyptic number.

21605859 is a deficient number, since it is larger than the sum of its proper divisors (14561181).

21605859 is a wasteful number, since it uses less digits than its factorization.

21605859 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222 (or 210 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 21605859 is about 4648.2103007502. The cubic root of 21605859 is about 278.5205083598.

The spelling of 21605859 in words is "twenty-one million, six hundred five thousand, eight hundred fifty-nine".