21289487 has 6 divisors (see below), whose sum is σ = 21512664. Its totient is φ = 21068600.

The previous prime is 21289459. The next prime is 21289493. The reversal of 21289487 is 78498212.

It is not a de Polignac number, because 21289487 - 2¹⁸ = 21027343 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 (21289447) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9158 + ... + 11244.

It is an arithmetic number, because the mean of its divisors is an integer number (3585444).

Almost surely, 2^21289487 is an apocalyptic number.

21289487 is a deficient number, since it is larger than the sum of its proper divisors (223177).

21289487 is an equidigital number, since it uses as much as digits as its factorization.

21289487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2289 (or 2188 counting only the distinct ones).

The product of its digits is 64512, while the sum is 41.

The square root of 21289487 is about 4614.0532073222. The cubic root of 21289487 is about 277.1543709821.

The spelling of 21289487 in words is "twenty-one million, two hundred eighty-nine thousand, four hundred eighty-seven".