21307573 has 4 divisors (see below), whose sum is σ = 24351520. Its totient is φ = 18263628.

The previous prime is 21307553. The next prime is 21307589. The reversal of 21307573 is 37570312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21307573 - 2¹³ = 21299381 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 (21307553) 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, 1521963 + ... + 1521976.

It is an arithmetic number, because the mean of its divisors is an integer number (6087880).

Almost surely, 2^21307573 is an apocalyptic number.

It is an amenable number.

21307573 is a deficient number, since it is larger than the sum of its proper divisors (3043947).

21307573 is an equidigital number, since it uses as much as digits as its factorization.

21307573 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3043946.

The product of its (nonzero) digits is 4410, while the sum is 28.

The square root of 21307573 is about 4616.0126732928. The cubic root of 21307573 is about 277.2328321677.

Adding to 21307573 its reverse (37570312), we get a palindrome (58877885).

The spelling of 21307573 in words is "twenty-one million, three hundred seven thousand, five hundred seventy-three".