21520249 has 12 divisors (see below), whose sum is σ = 23829876. Its totient is φ = 19365632.

The previous prime is 21520243. The next prime is 21520271. The reversal of 21520249 is 94202512.

It can be written as a sum of positive squares in 2 ways, for example, as 7118224 + 14402025 = 2668^2 + 3795^2 .

It is not a de Polignac number, because 21520249 - 2³ = 21520241 is a prime.

It is a super-2 number, since 2×21520249² = 926242234044002, which contains 22 as substring.

It is a Duffinian 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 11 ways as a sum of consecutive naturals, for example, 7797 + ... + 10189.

It is an arithmetic number, because the mean of its divisors is an integer number (1985823).

Almost surely, 2^21520249 is an apocalyptic number.

It is an amenable number.

21520249 is a deficient number, since it is larger than the sum of its proper divisors (2309627).

21520249 is a wasteful number, since it uses less digits than its factorization.

21520249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2456 (or 2433 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21520249 is about 4638.9922397003. The cubic root of 21520249 is about 278.1521560657.

It can be divided in two parts, 2 and 1520249, that added together give a palindrome (1520251).

The spelling of 21520249 in words is "twenty-one million, five hundred twenty thousand, two hundred forty-nine".