21518163 has 8 divisors (see below), whose sum is σ = 31878800. Its totient is φ = 14345424.

The previous prime is 21518143. The next prime is 21518197. The reversal of 21518163 is 36181512.

It is not a de Polignac number, because 21518163 - 2⁵ = 21518131 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 796969 = 21518163 / (2 + 1 + 5 + 1 + 8 + 1 + 6 + 3).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21518143) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 398458 + ... + 398511.

It is an arithmetic number, because the mean of its divisors is an integer number (3984850).

Almost surely, 2^21518163 is an apocalyptic number.

21518163 is a deficient number, since it is larger than the sum of its proper divisors (10360637).

21518163 is an equidigital number, since it uses as much as digits as its factorization.

21518163 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 796978 (or 796972 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 21518163 is about 4638.7674009375. The cubic root of 21518163 is about 278.1431684971.

Adding to 21518163 its reverse (36181512), we get a palindrome (57699675).

The spelling of 21518163 in words is "twenty-one million, five hundred eighteen thousand, one hundred sixty-three".