21749715 has 80 divisors (see below), whose sum is σ = 44640288. Its totient is φ = 10077696.

The previous prime is 21749713. The next prime is 21749719. The reversal of 21749715 is 51794712.

It is a happy number.

It is not a de Polignac number, because 21749715 - 2¹ = 21749713 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21749715.

It is not an unprimeable number, because it can be changed into a prime (21749713) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 1279387 + ... + 1279403.

Almost surely, 2^21749715 is an apocalyptic number.

21749715 is an abundant number, since it is smaller than the sum of its proper divisors (22890573).

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

21749715 is an frugal number, since it uses more digits than its factorization.

21749715 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62 (or 38 counting only the distinct ones).

The product of its digits is 17640, while the sum is 36.

The square root of 21749715 is about 4663.6589712371. The cubic root of 21749715 is about 279.1372893519.

The spelling of 21749715 in words is "twenty-one million, seven hundred forty-nine thousand, seven hundred fifteen".