21689985 has 16 divisors (see below), whose sum is σ = 35360064. Its totient is φ = 11349312.

The previous prime is 21689981. The next prime is 21690013. The reversal of 21689985 is 58998612.

It is a happy number.

It is not a de Polignac number, because 21689985 - 2² = 21689981 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21689981) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12847 + ... + 14436.

It is an arithmetic number, because the mean of its divisors is an integer number (2210004).

Almost surely, 2^21689985 is an apocalyptic number.

It is an amenable number.

21689985 is a deficient number, since it is larger than the sum of its proper divisors (13670079).

21689985 is a wasteful number, since it uses less digits than its factorization.

21689985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27344.

The product of its digits is 311040, while the sum is 48.

The square root of 21689985 is about 4657.2507984862. The cubic root of 21689985 is about 278.8815288174.

The spelling of 21689985 in words is "twenty-one million, six hundred eighty-nine thousand, nine hundred eighty-five".