21516049 has 4 divisors (see below), whose sum is σ = 21533220. Its totient is φ = 21498880.

The previous prime is 21516041. The next prime is 21516071. The reversal of 21516049 is 94061512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1979649 + 19536400 = 1407^2 + 4420^2 .

It is a cyclic number.

It is not a de Polignac number, because 21516049 - 2³ = 21516041 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21516041) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6544 + ... + 9265.

It is an arithmetic number, because the mean of its divisors is an integer number (5383305).

Almost surely, 2^21516049 is an apocalyptic number.

It is an amenable number.

21516049 is a deficient number, since it is larger than the sum of its proper divisors (17171).

21516049 is a wasteful number, since it uses less digits than its factorization.

21516049 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17170.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21516049 is about 4638.5395330858. The cubic root of 21516049 is about 278.1340596973.

The spelling of 21516049 in words is "twenty-one million, five hundred sixteen thousand, forty-nine".