21687634 has 8 divisors (see below), whose sum is σ = 32612220. Its totient is φ = 10816896.

The previous prime is 21687623. The next prime is 21687641. The reversal of 21687634 is 43678612.

21687634 = T₉₉ + T₁₀₀ + ... + T₅₀₇.

It can be written as a sum of positive squares in 2 ways, for example, as 21594609 + 93025 = 4647^2 + 305^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 21687593 and 21687602.

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 3 ways as a sum of consecutive naturals, for example, 12439 + ... + 14074.

Almost surely, 2^21687634 is an apocalyptic number.

21687634 is a deficient number, since it is larger than the sum of its proper divisors (10924586).

21687634 is a wasteful number, since it uses less digits than its factorization.

21687634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26924.

The product of its digits is 48384, while the sum is 37.

The square root of 21687634 is about 4656.9983895209. The cubic root of 21687634 is about 278.8714523671.

The spelling of 21687634 in words is "twenty-one million, six hundred eighty-seven thousand, six hundred thirty-four".