21427487 has 4 divisors (see below), whose sum is σ = 21438936. Its totient is φ = 21416040.

The previous prime is 21427481. The next prime is 21427489. The reversal of 21427487 is 78472412.

It is a happy number.

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 is a cyclic number.

It is not a de Polignac number, because 21427487 - 2¹⁰ = 21426463 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 (21427481) 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, 2189 + ... + 6902.

It is an arithmetic number, because the mean of its divisors is an integer number (5359734).

Almost surely, 2^21427487 is an apocalyptic number.

21427487 is a deficient number, since it is larger than the sum of its proper divisors (11449).

21427487 is an equidigital number, since it uses as much as digits as its factorization.

21427487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11448.

The product of its digits is 25088, while the sum is 35.

The square root of 21427487 is about 4628.9833657079. The cubic root of 21427487 is about 277.7519266194.

Adding to 21427487 its reverse (78472412), we get a palindrome (99899899).

The spelling of 21427487 in words is "twenty-one million, four hundred twenty-seven thousand, four hundred eighty-seven".