21180243 has 16 divisors (see below), whose sum is σ = 33148160. Its totient is φ = 11775456.

The previous prime is 21180239. The next prime is 21180281. The reversal of 21180243 is 34208112.

It is not a de Polignac number, because 21180243 - 2² = 21180239 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21180043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12853 + ... + 14406.

It is an arithmetic number, because the mean of its divisors is an integer number (2071760).

Almost surely, 2^21180243 is an apocalyptic number.

21180243 is a deficient number, since it is larger than the sum of its proper divisors (11967917).

21180243 is a wasteful number, since it uses less digits than its factorization.

21180243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27306.

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21180243 is about 4602.1998000956. The cubic root of 21180243 is about 276.6794982839.

Adding to 21180243 its reverse (34208112), we get a palindrome (55388355).

The spelling of 21180243 in words is "twenty-one million, one hundred eighty thousand, two hundred forty-three".