21542166 has 32 divisors (see below), whose sum is σ = 48046080. Its totient is φ = 7154568.

The previous prime is 21542161. The next prime is 21542167. The reversal of 21542166 is 66124512.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19275 + ... + 20361.

It is an arithmetic number, because the mean of its divisors is an integer number (1501440).

Almost surely, 2^21542166 is an apocalyptic number.

21542166 is an abundant number, since it is smaller than the sum of its proper divisors (26503914).

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

21542166 is a wasteful number, since it uses less digits than its factorization.

21542166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1465 (or 1459 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21542166 is about 4641.3538973019. The cubic root of 21542166 is about 278.2465507670.

Adding to 21542166 its reverse (66124512), we get a palindrome (87666678).

The spelling of 21542166 in words is "twenty-one million, five hundred forty-two thousand, one hundred sixty-six".