21819993 has 16 divisors (see below), whose sum is σ = 33175296. Its totient is φ = 12637440.

The previous prime is 21819991. The next prime is 21820013. The reversal of 21819993 is 39991812.

It is not a de Polignac number, because 21819993 - 2¹ = 21819991 is a prime.

It is a super-2 number, since 2×21819993² = 952224189040098, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21819991) 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, 15793 + ... + 17118.

It is an arithmetic number, because the mean of its divisors is an integer number (2073456).

Almost surely, 2^21819993 is an apocalyptic number.

It is an amenable number.

21819993 is a deficient number, since it is larger than the sum of its proper divisors (11355303).

21819993 is a wasteful number, since it uses less digits than its factorization.

21819993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32944.

The product of its digits is 34992, while the sum is 42.

The square root of 21819993 is about 4671.1875363766. The cubic root of 21819993 is about 279.4376169521.

The spelling of 21819993 in words is "twenty-one million, eight hundred nineteen thousand, nine hundred ninety-three".