21381871 has 4 divisors (see below), whose sum is σ = 24436432. Its totient is φ = 18327312.

The previous prime is 21381853. The next prime is 21381887. The reversal of 21381871 is 17818312.

It is a happy number.

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 21381871 - 2⁵ = 21381839 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381071) 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 3 ways as a sum of consecutive naturals, for example, 1527270 + ... + 1527283.

It is an arithmetic number, because the mean of its divisors is an integer number (6109108).

Almost surely, 2^21381871 is an apocalyptic number.

21381871 is a deficient number, since it is larger than the sum of its proper divisors (3054561).

21381871 is an equidigital number, since it uses as much as digits as its factorization.

21381871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3054560.

The product of its digits is 2688, while the sum is 31.

The square root of 21381871 is about 4624.0535247767. The cubic root of 21381871 is about 277.5546887858.

The spelling of 21381871 in words is "twenty-one million, three hundred eighty-one thousand, eight hundred seventy-one".