21554166 has 16 divisors (see below), whose sum is σ = 43250688. Its totient is φ = 7161000.

The previous prime is 21554161. The next prime is 21554173. The reversal of 21554166 is 66145512.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21554161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3910 + ... + 7641.

It is an arithmetic number, because the mean of its divisors is an integer number (2703168).

Almost surely, 2^21554166 is an apocalyptic number.

21554166 is an abundant number, since it is smaller than the sum of its proper divisors (21696522).

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

21554166 is a wasteful number, since it uses less digits than its factorization.

21554166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11867.

The product of its digits is 7200, while the sum is 30.

The square root of 21554166 is about 4642.6464435707. The cubic root of 21554166 is about 278.2982066499.

Adding to 21554166 its reverse (66145512), we get a palindrome (87699678).

The spelling of 21554166 in words is "twenty-one million, five hundred fifty-four thousand, one hundred sixty-six".