21201660 has 36 divisors (see below), whose sum is σ = 64312248. Its totient is φ = 5653728.

The previous prime is 21201647. The next prime is 21201673. The reversal of 21201660 is 6610212.

It is a happy number.

21201660 is a `hidden beast` number, since 2 + 1 + 2 + 0 + 1 + 660 = 666.

It is an interprime number because it is at equal distance from previous prime (21201647) and next prime (21201673).

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 58714 + ... + 59073.

Almost surely, 2^21201660 is an apocalyptic number.

21201660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21201660 is an abundant number, since it is smaller than the sum of its proper divisors (43110588).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21201660 is a wasteful number, since it uses less digits than its factorization.

21201660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117802 (or 117797 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21201660 is about 4604.5260342407. The cubic root of 21201660 is about 276.7727242940.

Adding to 21201660 its reverse (6610212), we get a palindrome (27811872).

The spelling of 21201660 in words is "twenty-one million, two hundred one thousand, six hundred sixty".