21558973 has 2 divisors, whose sum is σ = 21558974. Its totient is φ = 21558972.

The previous prime is 21558961. The next prime is 21558997. The reversal of 21558973 is 37985512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18645124 + 2913849 = 4318^2 + 1707^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21558973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21558913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10779486 + 10779487.

It is an arithmetic number, because the mean of its divisors is an integer number (10779487).

Almost surely, 2^21558973 is an apocalyptic number.

It is an amenable number.

21558973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21558973 is an equidigital number, since it uses as much as digits as its factorization.

21558973 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 75600, while the sum is 40.

The square root of 21558973 is about 4643.1641151267. The cubic root of 21558973 is about 278.3188937573.

The spelling of 21558973 in words is "twenty-one million, five hundred fifty-eight thousand, nine hundred seventy-three".