21616949 has 2 divisors, whose sum is σ = 21616950. Its totient is φ = 21616948.

The previous prime is 21616939. The next prime is 21616957. The reversal of 21616949 is 94961612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20160100 + 1456849 = 4490^2 + 1207^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21616949 is a prime.

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 (21616909) 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, 10808474 + 10808475.

It is an arithmetic number, because the mean of its divisors is an integer number (10808475).

Almost surely, 2^21616949 is an apocalyptic number.

It is an amenable number.

21616949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21616949 is an equidigital number, since it uses as much as digits as its factorization.

21616949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 38.

The square root of 21616949 is about 4649.4030799663. The cubic root of 21616949 is about 278.5681538327.

The spelling of 21616949 in words is "twenty-one million, six hundred sixteen thousand, nine hundred forty-nine".