21804071 has 4 divisors (see below), whose sum is σ = 21819144. Its totient is φ = 21789000.

The previous prime is 21804043. The next prime is 21804073. The reversal of 21804071 is 17040812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21804071 - 2⁶ = 21804007 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21804073) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5105 + ... + 8346.

It is an arithmetic number, because the mean of its divisors is an integer number (5454786).

Almost surely, 2^21804071 is an apocalyptic number.

21804071 is a deficient number, since it is larger than the sum of its proper divisors (15073).

21804071 is a wasteful number, since it uses less digits than its factorization.

21804071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15072.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21804071 is about 4669.4829478220. The cubic root of 21804071 is about 279.3696320789.

Adding to 21804071 its reverse (17040812), we get a palindrome (38844883).

The spelling of 21804071 in words is "twenty-one million, eight hundred four thousand, seventy-one".