21180919 has 4 divisors (see below), whose sum is σ = 21213720. Its totient is φ = 21148120.

The previous prime is 21180917. The next prime is 21180923. The reversal of 21180919 is 91908112.

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

It is a cyclic number.

It is not a de Polignac number, because 21180919 - 2¹ = 21180917 is a prime.

It is a super-2 number, since 2×21180919² = 897262659369122, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21180917) 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, 15412 + ... + 16729.

It is an arithmetic number, because the mean of its divisors is an integer number (5303430).

Almost surely, 2^21180919 is an apocalyptic number.

21180919 is a deficient number, since it is larger than the sum of its proper divisors (32801).

21180919 is an equidigital number, since it uses as much as digits as its factorization.

21180919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32800.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 21180919 is about 4602.2732426487. The cubic root of 21180919 is about 276.6824418030.

The spelling of 21180919 in words is "twenty-one million, one hundred eighty thousand, nine hundred nineteen".