21687024 has 40 divisors (see below), whose sum is σ = 56339152. Its totient is φ = 7188480.

The previous prime is 21686989. The next prime is 21687077. The reversal of 21687024 is 42078612.

It is a junction number, because it is equal to n+sod(n) for n = 21686982 and 21687000.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8094 + ... + 10434.

Almost surely, 2^21687024 is an apocalyptic number.

21687024 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21687024 is an abundant number, since it is smaller than the sum of its proper divisors (34652128).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21687024 is a wasteful number, since it uses less digits than its factorization.

21687024 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2545 (or 2539 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21687024 is about 4656.9328962312. The cubic root of 21687024 is about 278.8688377714.

The spelling of 21687024 in words is "twenty-one million, six hundred eighty-seven thousand, twenty-four".