21812247 has 20 divisors (see below), whose sum is σ = 34301080. Its totient is φ = 13775184.

The previous prime is 21812239. The next prime is 21812249. The reversal of 21812247 is 74221812.

It is not a de Polignac number, because 21812247 - 2³ = 21812239 is a prime.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21812247.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21812249) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 5548 + ... + 8625.

It is an arithmetic number, because the mean of its divisors is an integer number (1715054).

Almost surely, 2^21812247 is an apocalyptic number.

21812247 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21812247 is a deficient number, since it is larger than the sum of its proper divisors (12488833).

21812247 is a wasteful number, since it uses less digits than its factorization.

21812247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14204 (or 14195 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 21812247 is about 4670.3583374298. The cubic root of 21812247 is about 279.4045466701.

The spelling of 21812247 in words is "twenty-one million, eight hundred twelve thousand, two hundred forty-seven".