21565273 has 2 divisors, whose sum is σ = 21565274. Its totient is φ = 21565272.

The previous prime is 21565261. The next prime is 21565277. The reversal of 21565273 is 37256512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21501769 + 63504 = 4637^2 + 252^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21565273 is a prime.

It is not a weakly prime, because it can be changed into another prime (21565277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10782636 + 10782637.

It is an arithmetic number, because the mean of its divisors is an integer number (10782637).

Almost surely, 2^21565273 is an apocalyptic number.

It is an amenable number.

21565273 is a deficient number, since it is larger than the sum of its proper divisors (1).

21565273 is an equidigital number, since it uses as much as digits as its factorization.

21565273 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12600, while the sum is 31.

The square root of 21565273 is about 4643.8424822554. The cubic root of 21565273 is about 278.3460013915.

The spelling of 21565273 in words is "twenty-one million, five hundred sixty-five thousand, two hundred seventy-three".