21487897 has 4 divisors (see below), whose sum is σ = 21499060. Its totient is φ = 21476736.

The previous prime is 21487891. The next prime is 21487919. The reversal of 21487897 is 79878412.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 17816841 + 3671056 = 4221^2 + 1916^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21487897 is a prime.

It is a super-3 number, since 3×21487897³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21487891) 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, 1872 + ... + 6817.

It is an arithmetic number, because the mean of its divisors is an integer number (5374765).

Almost surely, 2^21487897 is an apocalyptic number.

It is an amenable number.

21487897 is a deficient number, since it is larger than the sum of its proper divisors (11163).

21487897 is an equidigital number, since it uses as much as digits as its factorization.

21487897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11162.

The product of its digits is 225792, while the sum is 46.

The square root of 21487897 is about 4635.5039639720. The cubic root of 21487897 is about 278.0127014882.

The spelling of 21487897 in words is "twenty-one million, four hundred eighty-seven thousand, eight hundred ninety-seven".