21135973 has 4 divisors (see below), whose sum is σ = 21184128. Its totient is φ = 21087820.

The previous prime is 21135971. The next prime is 21135997. The reversal of 21135973 is 37953112.

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 21135973 - 2¹ = 21135971 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135971) 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, 23413 + ... + 24298.

It is an arithmetic number, because the mean of its divisors is an integer number (5296032).

Almost surely, 2^21135973 is an apocalyptic number.

It is an amenable number.

21135973 is a deficient number, since it is larger than the sum of its proper divisors (48155).

21135973 is an equidigital number, since it uses as much as digits as its factorization.

21135973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48154.

The product of its digits is 5670, while the sum is 31.

The square root of 21135973 is about 4597.3876277730. The cubic root of 21135973 is about 276.4865961040.

The spelling of 21135973 in words is "twenty-one million, one hundred thirty-five thousand, nine hundred seventy-three".