21100985 has 8 divisors (see below), whose sum is σ = 25421256. Its totient is φ = 16814080.

The previous prime is 21100969. The next prime is 21100993. The reversal of 21100985 is 58900112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1951609 + 19149376 = 1397^2 + 4376^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21100985 - 2⁴ = 21100969 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6926 + ... + 9495.

It is an arithmetic number, because the mean of its divisors is an integer number (3177657).

Almost surely, 2^21100985 is an apocalyptic number.

It is an amenable number.

21100985 is a deficient number, since it is larger than the sum of its proper divisors (4320271).

21100985 is a wasteful number, since it uses less digits than its factorization.

21100985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16683.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 21100985 is about 4593.5808472258. The cubic root of 21100985 is about 276.3339486749. Note that the first 3 decimals are identical.

The spelling of 21100985 in words is "twenty-one million, one hundred thousand, nine hundred eighty-five".