21918043 has 8 divisors (see below), whose sum is σ = 25560800. Its totient is φ = 18786600.

The previous prime is 21918037. The next prime is 21918053. The reversal of 21918043 is 34081912.

It is a happy number.

It is not a de Polignac number, because 21918043 - 2¹⁷ = 21786971 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21918053) 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, 31608 + ... + 32293.

It is an arithmetic number, because the mean of its divisors is an integer number (3195100).

Almost surely, 2^21918043 is an apocalyptic number.

21918043 is a deficient number, since it is larger than the sum of its proper divisors (3642757).

21918043 is an frugal number, since it uses more digits than its factorization.

21918043 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63922 (or 63908 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21918043 is about 4681.6709623808. The cubic root of 21918043 is about 279.8555504926.

Adding to 21918043 its reverse (34081912), we get a palindrome (55999955).

The spelling of 21918043 in words is "twenty-one million, nine hundred eighteen thousand, forty-three".