21289287 has 8 divisors (see below), whose sum is σ = 30055536. Its totient is φ = 13357952.

The previous prime is 21289273. The next prime is 21289297. The reversal of 21289287 is 78298212.

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 21289287 - 2⁴ = 21289271 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21289297) 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, 208668 + ... + 208769.

It is an arithmetic number, because the mean of its divisors is an integer number (3756942).

Almost surely, 2^21289287 is an apocalyptic number.

21289287 is a deficient number, since it is larger than the sum of its proper divisors (8766249).

21289287 is a wasteful number, since it uses less digits than its factorization.

21289287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 417457.

The product of its digits is 32256, while the sum is 39.

The square root of 21289287 is about 4614.0315343526. The cubic root of 21289287 is about 277.1535030882.

The spelling of 21289287 in words is "twenty-one million, two hundred eighty-nine thousand, two hundred eighty-seven".