21820234 has 4 divisors (see below), whose sum is σ = 32730354. Its totient is φ = 10910116.

The previous prime is 21820213. The next prime is 21820243. The reversal of 21820234 is 43202812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21594609 + 225625 = 4647^2 + 475^2 .

It is a super-2 number, since 2×21820234² = 952245223629512, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5455057 + ... + 5455060.

Almost surely, 2^21820234 is an apocalyptic number.

21820234 is a deficient number, since it is larger than the sum of its proper divisors (10910120).

21820234 is a wasteful number, since it uses less digits than its factorization.

21820234 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10910119.

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 21820234 is about 4671.2133327434. The cubic root of 21820234 is about 279.4386457367.

The spelling of 21820234 in words is "twenty-one million, eight hundred twenty thousand, two hundred thirty-four".