21812071 has 4 divisors (see below), whose sum is σ = 23095152. Its totient is φ = 20528992.

The previous prime is 21812069. The next prime is 21812081. The reversal of 21812071 is 17021812.

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 21812071 - 2¹ = 21812069 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 (21812081) 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, 641515 + ... + 641548.

It is an arithmetic number, because the mean of its divisors is an integer number (5773788).

Almost surely, 2^21812071 is an apocalyptic number.

21812071 is a deficient number, since it is larger than the sum of its proper divisors (1283081).

21812071 is a wasteful number, since it uses less digits than its factorization.

21812071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1283080.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21812071 is about 4670.3394951545. The cubic root of 21812071 is about 279.4037951759.

Adding to 21812071 its reverse (17021812), we get a palindrome (38833883).

The spelling of 21812071 in words is "twenty-one million, eight hundred twelve thousand, seventy-one".