21439081 has 4 divisors (see below), whose sum is σ = 21518464. Its totient is φ = 21359700.

The previous prime is 21439079. The next prime is 21439109. The reversal of 21439081 is 18093412.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21439081 - 2¹ = 21439079 is a prime.

It is a super-2 number, since 2×21439081² = 919268388249122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21439981) 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, 39285 + ... + 39826.

It is an arithmetic number, because the mean of its divisors is an integer number (5379616).

Almost surely, 2^21439081 is an apocalyptic number.

It is an amenable number.

21439081 is a deficient number, since it is larger than the sum of its proper divisors (79383).

21439081 is an equidigital number, since it uses as much as digits as its factorization.

21439081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79382.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21439081 is about 4630.2355231673. The cubic root of 21439081 is about 277.8020129907.

The spelling of 21439081 in words is "twenty-one million, four hundred thirty-nine thousand, eighty-one".