21673513 has 4 divisors (see below), whose sum is σ = 21865428. Its totient is φ = 21481600.

The previous prime is 21673511. The next prime is 21673517. The reversal of 21673513 is 31537612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 218089 + 21455424 = 467^2 + 4632^2 .

It is a cyclic number.

It is not a de Polignac number, because 21673513 - 2¹ = 21673511 is a prime.

It is a super-2 number, since 2×21673513² = 939482331522338, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21673511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 95788 + ... + 96013.

It is an arithmetic number, because the mean of its divisors is an integer number (5466357).

Almost surely, 2^21673513 is an apocalyptic number.

It is an amenable number.

21673513 is a deficient number, since it is larger than the sum of its proper divisors (191915).

21673513 is a wasteful number, since it uses less digits than its factorization.

21673513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191914.

The product of its digits is 3780, while the sum is 28.

The square root of 21673513 is about 4655.4820373405. The cubic root of 21673513 is about 278.8109140474.

The spelling of 21673513 in words is "twenty-one million, six hundred seventy-three thousand, five hundred thirteen".