21686474 has 4 divisors (see below), whose sum is σ = 32529714. Its totient is φ = 10843236.

The previous prime is 21686473. The next prime is 21686479. The reversal of 21686474 is 47468612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 15960025 + 5726449 = 3995^2 + 2393^2 .

It is not an unprimeable number, because it can be changed into a prime (21686471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5421617 + ... + 5421620.

Almost surely, 2^21686474 is an apocalyptic number.

21686474 is a deficient number, since it is larger than the sum of its proper divisors (10843240).

21686474 is a wasteful number, since it uses less digits than its factorization.

21686474 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10843239.

The product of its digits is 64512, while the sum is 38.

The square root of 21686474 is about 4656.8738441147. The cubic root of 21686474 is about 278.8664803071.

The spelling of 21686474 in words is "twenty-one million, six hundred eighty-six thousand, four hundred seventy-four".