21520245 has 16 divisors (see below), whose sum is σ = 34490880. Its totient is φ = 11457984.

The previous prime is 21520243. The next prime is 21520271. The reversal of 21520245 is 54202512.

It is a happy number.

It is not a de Polignac number, because 21520245 - 2¹ = 21520243 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14236 + ... + 15674.

It is an arithmetic number, because the mean of its divisors is an integer number (2155680).

Almost surely, 2^21520245 is an apocalyptic number.

It is an amenable number.

21520245 is a deficient number, since it is larger than the sum of its proper divisors (12970635).

21520245 is a wasteful number, since it uses less digits than its factorization.

21520245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2444.

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21520245 is about 4638.9918085722. The cubic root of 21520245 is about 278.1521388322.

Adding to 21520245 its reverse (54202512), we get a palindrome (75722757).

The spelling of 21520245 in words is "twenty-one million, five hundred twenty thousand, two hundred forty-five".