21697853 has 2 divisors, whose sum is σ = 21697854. Its totient is φ = 21697852.

The previous prime is 21697847. The next prime is 21697889. The reversal of 21697853 is 35879612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15031129 + 6666724 = 3877^2 + 2582^2 .

It is a cyclic number.

It is not a de Polignac number, because 21697853 - 2⁶ = 21697789 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21697853.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21697153) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10848926 + 10848927.

It is an arithmetic number, because the mean of its divisors is an integer number (10848927).

Almost surely, 2^21697853 is an apocalyptic number.

It is an amenable number.

21697853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21697853 is an equidigital number, since it uses as much as digits as its factorization.

21697853 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 41.

The square root of 21697853 is about 4658.0954262445. The cubic root of 21697853 is about 278.9152459853.

The spelling of 21697853 in words is "twenty-one million, six hundred ninety-seven thousand, eight hundred fifty-three".