21856349 has 2 divisors, whose sum is σ = 21856350. Its totient is φ = 21856348.

The previous prime is 21856337. The next prime is 21856357. The reversal of 21856349 is 94365812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13271449 + 8584900 = 3643^2 + 2930^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21856349 is a prime.

It is a super-3 number, since 3×21856349³ (a number of 23 digits) contains 333 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21856379) 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, 10928174 + 10928175.

It is an arithmetic number, because the mean of its divisors is an integer number (10928175).

Almost surely, 2^21856349 is an apocalyptic number.

It is an amenable number.

21856349 is a deficient number, since it is larger than the sum of its proper divisors (1).

21856349 is an equidigital number, since it uses as much as digits as its factorization.

21856349 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 51840, while the sum is 38.

The square root of 21856349 is about 4675.0774325138. The cubic root of 21856349 is about 279.5927284722.

The spelling of 21856349 in words is "twenty-one million, eight hundred fifty-six thousand, three hundred forty-nine".