21153666 has 16 divisors (see below), whose sum is σ = 43208064. Its totient is φ = 6901104.

The previous prime is 21153653. The next prime is 21153689. The reversal of 21153666 is 66635112.

It is a Curzon 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, 37225 + ... + 37788.

It is an arithmetic number, because the mean of its divisors is an integer number (2700504).

Almost surely, 2^21153666 is an apocalyptic number.

21153666 is an abundant number, since it is smaller than the sum of its proper divisors (22054398).

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

21153666 is a wasteful number, since it uses less digits than its factorization.

21153666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75065.

The product of its digits is 6480, while the sum is 30.

The square root of 21153666 is about 4599.3114702094. The cubic root of 21153666 is about 276.5637238990.

Adding to 21153666 its reverse (66635112), we get a palindrome (87788778).

The spelling of 21153666 in words is "twenty-one million, one hundred fifty-three thousand, six hundred sixty-six".