21130181 has 4 divisors (see below), whose sum is σ = 21162252. Its totient is φ = 21098112.

The previous prime is 21130111. The next prime is 21130231. The reversal of 21130181 is 18103112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7924225 + 13205956 = 2815^2 + 3634^2 .

It is a cyclic number.

It is not a de Polignac number, because 21130181 - 2¹⁴ = 21113797 is a prime.

It is a super-2 number, since 2×21130181² = 892969098185522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21130111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15026 + ... + 16371.

It is an arithmetic number, because the mean of its divisors is an integer number (5290563).

Almost surely, 2^21130181 is an apocalyptic number.

It is an amenable number.

21130181 is a deficient number, since it is larger than the sum of its proper divisors (32071).

21130181 is an equidigital number, since it uses as much as digits as its factorization.

21130181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32070.

The product of its (nonzero) digits is 48, while the sum is 17.

The square root of 21130181 is about 4596.7576616567. The cubic root of 21130181 is about 276.4613381127.

Adding to 21130181 its reverse (18103112), we get a palindrome (39233293).

The spelling of 21130181 in words is "twenty-one million, one hundred thirty thousand, one hundred eighty-one".