21388949 has 2 divisors, whose sum is σ = 21388950. Its totient is φ = 21388948.

The previous prime is 21388943. The next prime is 21388957. The reversal of 21388949 is 94988312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16957924 + 4431025 = 4118^2 + 2105^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388949 - 2²⁰ = 20340373 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21388943) 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, 10694474 + 10694475.

It is an arithmetic number, because the mean of its divisors is an integer number (10694475).

Almost surely, 2^21388949 is an apocalyptic number.

It is an amenable number.

21388949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388949 is an equidigital number, since it uses as much as digits as its factorization.

21388949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 44.

The square root of 21388949 is about 4624.8188072615. The cubic root of 21388949 is about 277.5853115403.

The spelling of 21388949 in words is "twenty-one million, three hundred eighty-eight thousand, nine hundred forty-nine".