21821427 has 36 divisors (see below), whose sum is σ = 34596120. Its totient is φ = 13592880.

The previous prime is 21821419. The next prime is 21821441. The reversal of 21821427 is 72412812.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

21821427 is a `hidden beast` number, since 218 + 21 + 427 = 666.

It is not a de Polignac number, because 21821427 - 2³ = 21821419 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 21821427.

It is not an unprimeable number, because it can be changed into a prime (21821027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 703902 + ... + 703932.

Almost surely, 2^21821427 is an apocalyptic number.

21821427 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21821427 is a deficient number, since it is larger than the sum of its proper divisors (12774693).

21821427 is an equidigital number, since it uses as much as digits as its factorization.

21821427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129 (or 63 counting only the distinct ones).

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

The square root of 21821427 is about 4671.3410280133. The cubic root of 21821427 is about 279.4437383223.

Multiplying 21821427 by its sum of digits (27), we get a square (589178529 = 24273²).

21821427 divided by its sum of digits (27) gives a square (808201 = 899²).

The spelling of 21821427 in words is "twenty-one million, eight hundred twenty-one thousand, four hundred twenty-seven".