21345687 has 20 divisors (see below), whose sum is σ = 34787016. Its totient is φ = 12936240.

The previous prime is 21345637. The next prime is 21345703. The reversal of 21345687 is 78654312.

It is not a de Polignac number, because 21345687 - 2⁸ = 21345431 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21345637) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 11088 + ... + 12869.

Almost surely, 2^21345687 is an apocalyptic number.

21345687 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21345687 is a deficient number, since it is larger than the sum of its proper divisors (13441329).

21345687 is a wasteful number, since it uses less digits than its factorization.

21345687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23980 (or 23971 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 21345687 is about 4620.1392836147. The cubic root of 21345687 is about 277.3980341229.

Adding to 21345687 its reverse (78654312), we get a palindrome (99999999).

The spelling of 21345687 in words is "twenty-one million, three hundred forty-five thousand, six hundred eighty-seven".