21352973 has 4 divisors (see below), whose sum is σ = 21363900. Its totient is φ = 21342048.

The previous prime is 21352963. The next prime is 21352987. The reversal of 21352973 is 37925312.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 11854249 + 9498724 = 3443^2 + 3082^2 .

It is a cyclic number.

It is not a de Polignac number, because 21352973 - 2¹⁴ = 21336589 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 (21352913) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1640 + ... + 6737.

It is an arithmetic number, because the mean of its divisors is an integer number (5340975).

Almost surely, 2^21352973 is an apocalyptic number.

It is an amenable number.

21352973 is a deficient number, since it is larger than the sum of its proper divisors (10927).

21352973 is an equidigital number, since it uses as much as digits as its factorization.

21352973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10926.

The product of its digits is 11340, while the sum is 32.

The square root of 21352973 is about 4620.9277207072. The cubic root of 21352973 is about 277.4295922883.

The spelling of 21352973 in words is "twenty-one million, three hundred fifty-two thousand, nine hundred seventy-three".