21731273 has 2 divisors, whose sum is σ = 21731274. Its totient is φ = 21731272.

The previous prime is 21731263. The next prime is 21731291. The reversal of 21731273 is 37213712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 644809 = 4592^2 + 803^2 .

It is a cyclic number.

It is not a de Polignac number, because 21731273 - 2⁴ = 21731257 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21731243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865636 + 10865637.

It is an arithmetic number, because the mean of its divisors is an integer number (10865637).

Almost surely, 2^21731273 is an apocalyptic number.

It is an amenable number.

21731273 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731273 is an equidigital number, since it uses as much as digits as its factorization.

21731273 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1764, while the sum is 26.

The square root of 21731273 is about 4661.6813490414. The cubic root of 21731273 is about 279.0583717575.

Adding to 21731273 its reverse (37213712), we get a palindrome (58944985).

The spelling of 21731273 in words is "twenty-one million, seven hundred thirty-one thousand, two hundred seventy-three".