21519673 has 18 divisors (see below), whose sum is σ = 25923258. Its totient is φ = 17811360.

The previous prime is 21519599. The next prime is 21519677. The reversal of 21519673 is 37691512.

It can be written as a sum of positive squares in only one way, i.e., 20766249 + 753424 = 4557^2 + 868^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21519673 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21519677) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 46861 + ... + 47317.

It is an arithmetic number, because the mean of its divisors is an integer number (1440181).

Almost surely, 2^21519673 is an apocalyptic number.

It is an amenable number.

21519673 is a deficient number, since it is larger than the sum of its proper divisors (4403585).

21519673 is an equidigital number, since it uses as much as digits as its factorization.

21519673 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 533 (or 495 counting only the distinct ones).

The product of its digits is 11340, while the sum is 34.

The square root of 21519673 is about 4638.9301568357. The cubic root of 21519673 is about 278.1496744174.

The spelling of 21519673 in words is "twenty-one million, five hundred nineteen thousand, six hundred seventy-three".