21687650 has 24 divisors (see below), whose sum is σ = 41732820. Its totient is φ = 8375360.

The previous prime is 21687641. The next prime is 21687691. The reversal of 21687650 is 5678612.

It is a Cunningham number, because it is equal to 4657²+1.

It can be written as a sum of positive squares in 6 ways, for example, as 5470921 + 16216729 = 2339^2 + 4027^2 .

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21687650.

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 11 ways as a sum of consecutive naturals, for example, 6029 + ... + 8928.

Almost surely, 2^21687650 is an apocalyptic number.

21687650 is a deficient number, since it is larger than the sum of its proper divisors (20045170).

21687650 is a wasteful number, since it uses less digits than its factorization.

21687650 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14998 (or 14993 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 21687650 is about 4657.0001073653. Note that the first 3 decimals coincide. The cubic root of 21687650 is about 278.8715209460.

The spelling of 21687650 in words is "twenty-one million, six hundred eighty-seven thousand, six hundred fifty".