21485813 has 2 divisors, whose sum is σ = 21485814. Its totient is φ = 21485812.

The previous prime is 21485809. The next prime is 21485819. The reversal of 21485813 is 31858412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16459249 + 5026564 = 4057^2 + 2242^2 .

It is a cyclic number.

It is not a de Polignac number, because 21485813 - 2² = 21485809 is a prime.

It is a plaindrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21485813.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21485819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10742906 + 10742907.

It is an arithmetic number, because the mean of its divisors is an integer number (10742907).

Almost surely, 2^21485813 is an apocalyptic number.

It is an amenable number.

21485813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21485813 is an equidigital number, since it uses as much as digits as its factorization.

21485813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7680, while the sum is 32.

The square root of 21485813 is about 4635.2791717436. The cubic root of 21485813 is about 278.0037135263.

The spelling of 21485813 in words is "twenty-one million, four hundred eighty-five thousand, eight hundred thirteen".