21028687 has 8 divisors (see below), whose sum is σ = 22467200. Its totient is φ = 19623384.

The previous prime is 21028673. The next prime is 21028697. The reversal of 21028687 is 78682012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21028687 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 (21028697) 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, 6987 + ... + 9532.

It is an arithmetic number, because the mean of its divisors is an integer number (2808400).

Almost surely, 2^21028687 is an apocalyptic number.

21028687 is a deficient number, since it is larger than the sum of its proper divisors (1438513).

21028687 is a wasteful number, since it uses less digits than its factorization.

21028687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16605.

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 21028687 is about 4585.7046350588. The cubic root of 21028687 is about 276.0179878706.

The spelling of 21028687 in words is "twenty-one million, twenty-eight thousand, six hundred eighty-seven".