21686842 has 8 divisors (see below), whose sum is σ = 33063732. Its totient is φ = 10665600.

The previous prime is 21686813. The next prime is 21686851. The reversal of 21686842 is 24868612.

It can be written as a sum of positive squares in 2 ways, for example, as 15531481 + 6155361 = 3941^2 + 2481^2 .

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

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, 88759 + ... + 89002.

Almost surely, 2^21686842 is an apocalyptic number.

21686842 is a deficient number, since it is larger than the sum of its proper divisors (11376890).

21686842 is a wasteful number, since it uses less digits than its factorization.

21686842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177824.

The product of its digits is 36864, while the sum is 37.

The square root of 21686842 is about 4656.9133554319. The cubic root of 21686842 is about 278.8680576695.

The spelling of 21686842 in words is "twenty-one million, six hundred eighty-six thousand, eight hundred forty-two".