21288973 has 2 divisors, whose sum is σ = 21288974. Its totient is φ = 21288972.

The previous prime is 21288959. The next prime is 21288983. The reversal of 21288973 is 37988212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14303524 + 6985449 = 3782^2 + 2643^2 .

It is a cyclic number.

It is not a de Polignac number, because 21288973 - 2⁹ = 21288461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21288923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10644486 + 10644487.

It is an arithmetic number, because the mean of its divisors is an integer number (10644487).

Almost surely, 2^21288973 is an apocalyptic number.

It is an amenable number.

21288973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21288973 is an equidigital number, since it uses as much as digits as its factorization.

21288973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48384, while the sum is 40.

The square root of 21288973 is about 4613.9975075849. The cubic root of 21288973 is about 277.1521404838.

The spelling of 21288973 in words is "twenty-one million, two hundred eighty-eight thousand, nine hundred seventy-three".