21381567 has 8 divisors (see below), whose sum is σ = 28530480. Its totient is φ = 14243520.

The previous prime is 21381557. The next prime is 21381611. The reversal of 21381567 is 76518312.

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

It is not a de Polignac number, because 21381567 - 2²² = 17187263 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381527) 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, 5059 + ... + 8267.

It is an arithmetic number, because the mean of its divisors is an integer number (3566310).

Almost surely, 2^21381567 is an apocalyptic number.

21381567 is a deficient number, since it is larger than the sum of its proper divisors (7148913).

21381567 is a wasteful number, since it uses less digits than its factorization.

21381567 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5433.

The product of its digits is 10080, while the sum is 33.

The square root of 21381567 is about 4624.0206530681. The cubic root of 21381567 is about 277.5533733876.

Adding to 21381567 its reverse (76518312), we get a palindrome (97899879).

The spelling of 21381567 in words is "twenty-one million, three hundred eighty-one thousand, five hundred sixty-seven".