21706253 has 2 divisors, whose sum is σ = 21706254. Its totient is φ = 21706252.

The previous prime is 21706241. The next prime is 21706259. The reversal of 21706253 is 35260712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16337764 + 5368489 = 4042^2 + 2317^2 .

It is a cyclic number.

It is not a de Polignac number, because 21706253 - 2¹² = 21702157 is a prime.

It is a super-2 number, since 2×21706253² = 942322838600018, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21706259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10853126 + 10853127.

It is an arithmetic number, because the mean of its divisors is an integer number (10853127).

Almost surely, 2^21706253 is an apocalyptic number.

It is an amenable number.

21706253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21706253 is an equidigital number, since it uses as much as digits as its factorization.

21706253 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 26.

The square root of 21706253 is about 4658.9969950623. The cubic root of 21706253 is about 278.9512339668.

Adding to 21706253 its reverse (35260712), we get a palindrome (56966965).

The spelling of 21706253 in words is "twenty-one million, seven hundred six thousand, two hundred fifty-three".