21193818 has 16 divisors (see below), whose sum is σ = 42465600. Its totient is φ = 7051616.

The previous prime is 21193817. The next prime is 21193819. The reversal of 21193818 is 81839112.

It is an interprime number because it is at equal distance from previous prime (21193817) and next prime (21193819).

It is not an unprimeable number, because it can be changed into a prime (21193813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 646 + ... + 6542.

It is an arithmetic number, because the mean of its divisors is an integer number (2654100).

Almost surely, 2^21193818 is an apocalyptic number.

21193818 is an abundant number, since it is smaller than the sum of its proper divisors (21271782).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21193818 is a wasteful number, since it uses less digits than its factorization.

21193818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6501.

The product of its digits is 3456, while the sum is 33.

The square root of 21193818 is about 4603.6744020402. The cubic root of 21193818 is about 276.7385961588.

The spelling of 21193818 in words is "twenty-one million, one hundred ninety-three thousand, eight hundred eighteen".