21681411 has 4 divisors (see below), whose sum is σ = 28908552. Its totient is φ = 14454272.

The previous prime is 21681389. The next prime is 21681421. The reversal of 21681411 is 11418612.

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 21681411 - 2⁶ = 21681347 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21681421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3613566 + ... + 3613571.

It is an arithmetic number, because the mean of its divisors is an integer number (7227138).

Almost surely, 2^21681411 is an apocalyptic number.

21681411 is a deficient number, since it is larger than the sum of its proper divisors (7227141).

21681411 is an equidigital number, since it uses as much as digits as its factorization.

21681411 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7227140.

The product of its digits is 384, while the sum is 24.

The square root of 21681411 is about 4656.3302073629. The cubic root of 21681411 is about 278.8447769037.

The spelling of 21681411 in words is "twenty-one million, six hundred eighty-one thousand, four hundred eleven".