21159999 has 48 divisors (see below), whose sum is σ = 36571392. Its totient is φ = 11539584.

The previous prime is 21159973. The next prime is 21160001. The reversal of 21159999 is 99995112.

It is a Cunningham number, because it is equal to 4600²-1.

It is not a de Polignac number, because 21159999 - 2⁹ = 21159487 is a prime.

21159999 is a modest number, since divided by 9999 gives 2115 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21159499) 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, 197704 + ... + 197810.

It is an arithmetic number, because the mean of its divisors is an integer number (761904).

Almost surely, 2^21159999 is an apocalyptic number.

21159999 is a deficient number, since it is larger than the sum of its proper divisors (15411393).

21159999 is a wasteful number, since it uses less digits than its factorization.

21159999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236 (or 233 counting only the distinct ones).

The product of its digits is 65610, while the sum is 45.

The square root of 21159999 is about 4599.9998913043. Note that the first 3 decimals coincide. The cubic root of 21159999 is about 276.5913204285.

The spelling of 21159999 in words is "twenty-one million, one hundred fifty-nine thousand, nine hundred ninety-nine".