21507073 has 4 divisors (see below), whose sum is σ = 24579520. Its totient is φ = 18434628.

The previous prime is 21507071. The next prime is 21507077. The reversal of 21507073 is 37070512.

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 21507073 - 2¹ = 21507071 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21507071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1536213 + ... + 1536226.

It is an arithmetic number, because the mean of its divisors is an integer number (6144880).

Almost surely, 2^21507073 is an apocalyptic number.

It is an amenable number.

21507073 is a deficient number, since it is larger than the sum of its proper divisors (3072447).

21507073 is an equidigital number, since it uses as much as digits as its factorization.

21507073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3072446.

The product of its (nonzero) digits is 1470, while the sum is 25.

The square root of 21507073 is about 4637.5718862353. The cubic root of 21507073 is about 278.0953772768.

Adding to 21507073 its reverse (37070512), we get a palindrome (58577585).

The spelling of 21507073 in words is "twenty-one million, five hundred seven thousand, seventy-three".