21805142 has 8 divisors (see below), whose sum is σ = 32874336. Its totient is φ = 10847032.

The previous prime is 21805139. The next prime is 21805159. The reversal of 21805142 is 24150812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27278 + ... + 28065.

It is an arithmetic number, because the mean of its divisors is an integer number (4109292).

Almost surely, 2^21805142 is an apocalyptic number.

21805142 is a deficient number, since it is larger than the sum of its proper divisors (11069194).

21805142 is a wasteful number, since it uses less digits than its factorization.

21805142 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55542.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21805142 is about 4669.5976272052. The cubic root of 21805142 is about 279.3742061480.

Adding to 21805142 its reverse (24150812), we get a palindrome (45955954).

The spelling of 21805142 in words is "twenty-one million, eight hundred five thousand, one hundred forty-two".