21516853 has 2 divisors, whose sum is σ = 21516854. Its totient is φ = 21516852.

The previous prime is 21516829. The next prime is 21516857. The reversal of 21516853 is 35861512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11135569 + 10381284 = 3337^2 + 3222^2 .

It is a cyclic number.

It is not a de Polignac number, because 21516853 - 2¹⁷ = 21385781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21516857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758426 + 10758427.

It is an arithmetic number, because the mean of its divisors is an integer number (10758427).

Almost surely, 2^21516853 is an apocalyptic number.

It is an amenable number.

21516853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516853 is an equidigital number, since it uses as much as digits as its factorization.

21516853 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7200, while the sum is 31.

The square root of 21516853 is about 4638.6261974856. The cubic root of 21516853 is about 278.1375240415.

The spelling of 21516853 in words is "twenty-one million, five hundred sixteen thousand, eight hundred fifty-three".