21812005 has 8 divisors (see below), whose sum is σ = 26618400. Its totient is φ = 17153616.

The previous prime is 21811987. The next prime is 21812017. The reversal of 21812005 is 50021812.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21812005 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36675 + ... + 37264.

It is an arithmetic number, because the mean of its divisors is an integer number (3327300).

Almost surely, 2^21812005 is an apocalyptic number.

It is an amenable number.

21812005 is a deficient number, since it is larger than the sum of its proper divisors (4806395).

21812005 is an equidigital number, since it uses as much as digits as its factorization.

21812005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74003.

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 21812005 is about 4670.3324292817. The cubic root of 21812005 is about 279.4035133645.

Adding to 21812005 its reverse (50021812), we get a palindrome (71833817).

It can be divided in two parts, 2181 and 2005, that added together give a triangular number (4186 = T₉₁).

The spelling of 21812005 in words is "twenty-one million, eight hundred twelve thousand, five".