21180921 has 8 divisors (see below), whose sum is σ = 28428864. Its totient is φ = 14026800.

The previous prime is 21180917. The next prime is 21180923. The reversal of 21180921 is 12908112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21180921 - 2² = 21180917 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21180891 and 21180900.

It is not an unprimeable number, because it can be changed into a prime (21180923) 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 7 ways as a sum of consecutive naturals, for example, 22926 + ... + 23831.

It is an arithmetic number, because the mean of its divisors is an integer number (3553608).

Almost surely, 2^21180921 is an apocalyptic number.

It is an amenable number.

21180921 is a deficient number, since it is larger than the sum of its proper divisors (7247943).

21180921 is a wasteful number, since it uses less digits than its factorization.

21180921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46911.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 21180921 is about 4602.2734599326. The cubic root of 21180921 is about 276.6824505116.

The spelling of 21180921 in words is "twenty-one million, one hundred eighty thousand, nine hundred twenty-one".