21101985 has 32 divisors (see below), whose sum is σ = 38090880. Its totient is φ = 11081664.

The previous prime is 21101963. The next prime is 21102023. The reversal of 21101985 is 58910112.

It is not a de Polignac number, because 21101985 - 2¹² = 21097889 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7879 + ... + 10211.

It is an arithmetic number, because the mean of its divisors is an integer number (1190340).

Almost surely, 2^21101985 is an apocalyptic number.

It is an amenable number.

21101985 is a deficient number, since it is larger than the sum of its proper divisors (16988895).

21101985 is a wasteful number, since it uses less digits than its factorization.

21101985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2414 (or 2408 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 27.

The square root of 21101985 is about 4593.6896934817. The cubic root of 21101985 is about 276.3383138674.

It can be divided in two parts, 2110 and 1985, that added together give a triangular number (4095 = T₉₀).

The spelling of 21101985 in words is "twenty-one million, one hundred one thousand, nine hundred eighty-five".