21581279 has 8 divisors (see below), whose sum is σ = 23017680. Its totient is φ = 20163456.

The previous prime is 21581269. The next prime is 21581311. The reversal of 21581279 is 97218512.

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

It is a cyclic number.

It is not a de Polignac number, because 21581279 - 2⁸ = 21581023 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 (21581269) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2204 + ... + 6929.

It is an arithmetic number, because the mean of its divisors is an integer number (2877210).

Almost surely, 2^21581279 is an apocalyptic number.

21581279 is a deficient number, since it is larger than the sum of its proper divisors (1436401).

21581279 is a wasteful number, since it uses less digits than its factorization.

21581279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9289.

The product of its digits is 10080, while the sum is 35.

The square root of 21581279 is about 4645.5655199340. The cubic root of 21581279 is about 278.4148482565.

The spelling of 21581279 in words is "twenty-one million, five hundred eighty-one thousand, two hundred seventy-nine".