21578897 has 4 divisors (see below), whose sum is σ = 21986100. Its totient is φ = 21171696.

The previous prime is 21578863. The next prime is 21578903. The reversal of 21578897 is 79887512.

21578897 is nontrivially palindromic in base 8.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13278736 + 8300161 = 3644^2 + 2881^2 .

It is a cyclic number.

It is not a de Polignac number, because 21578897 - 2¹⁶ = 21513361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21578827) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 203522 + ... + 203627.

It is an arithmetic number, because the mean of its divisors is an integer number (5496525).

Almost surely, 2^21578897 is an apocalyptic number.

It is an amenable number.

21578897 is a deficient number, since it is larger than the sum of its proper divisors (407203).

21578897 is an equidigital number, since it uses as much as digits as its factorization.

21578897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407202.

The product of its digits is 282240, while the sum is 47.

The square root of 21578897 is about 4645.3091393362. The cubic root of 21578897 is about 278.4046046782.

The spelling of 21578897 in words is "twenty-one million, five hundred seventy-eight thousand, eight hundred ninety-seven".