21749619 has 4 divisors (see below), whose sum is σ = 28999496. Its totient is φ = 14499744.

The previous prime is 21749617. The next prime is 21749621. The reversal of 21749619 is 91694712.

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

It is an interprime number because it is at equal distance from previous prime (21749617) and next prime (21749621).

It is not a de Polignac number, because 21749619 - 2¹ = 21749617 is a prime.

It is a super-2 number, since 2×21749619² = 946091853290322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21749617) 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 3 ways as a sum of consecutive naturals, for example, 3624934 + ... + 3624939.

It is an arithmetic number, because the mean of its divisors is an integer number (7249874).

Almost surely, 2^21749619 is an apocalyptic number.

21749619 is a deficient number, since it is larger than the sum of its proper divisors (7249877).

21749619 is an equidigital number, since it uses as much as digits as its factorization.

21749619 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7249876.

The product of its digits is 27216, while the sum is 39.

The square root of 21749619 is about 4663.6486788779. The cubic root of 21749619 is about 279.1368786612.

The spelling of 21749619 in words is "twenty-one million, seven hundred forty-nine thousand, six hundred nineteen".