21651853 has 2 divisors, whose sum is σ = 21651854. Its totient is φ = 21651852.

The previous prime is 21651841. The next prime is 21651859. The reversal of 21651853 is 35815612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21650409 + 1444 = 4653^2 + 38^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21651853 is a prime.

It is equal to p_1368562 and since 21651853 and 1368562 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21651859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825926 + 10825927.

It is an arithmetic number, because the mean of its divisors is an integer number (10825927).

Almost surely, 2^21651853 is an apocalyptic number.

It is an amenable number.

21651853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651853 is an equidigital number, since it uses as much as digits as its factorization.

21651853 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21651853 is about 4653.1551661212. The cubic root of 21651853 is about 278.7180040628.

The spelling of 21651853 in words is "twenty-one million, six hundred fifty-one thousand, eight hundred fifty-three".