21818539 has 2 divisors, whose sum is σ = 21818540. Its totient is φ = 21818538.

The previous prime is 21818521. The next prime is 21818557. The reversal of 21818539 is 93581812.

It is a balanced prime because it is at equal distance from previous prime (21818521) and next prime (21818557).

It is a cyclic number.

It is not a de Polignac number, because 21818539 - 2⁵ = 21818507 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21818498 and 21818507.

It is not a weakly prime, because it can be changed into another prime (21818569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909269 + 10909270.

It is an arithmetic number, because the mean of its divisors is an integer number (10909270).

Almost surely, 2^21818539 is an apocalyptic number.

21818539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21818539 is an equidigital number, since it uses as much as digits as its factorization.

21818539 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17280, while the sum is 37.

The square root of 21818539 is about 4671.0318988421. The cubic root of 21818539 is about 279.4314099333.

It can be divided in two parts, 21 and 818539, that added together give a triangular number (818560 = T₁₂₇₉).

The spelling of 21818539 in words is "twenty-one million, eight hundred eighteen thousand, five hundred thirty-nine".