21051245 has 16 divisors (see below), whose sum is σ = 26777520. Its totient is φ = 15859200.

The previous prime is 21051241. The next prime is 21051257. The reversal of 21051245 is 54215012.

It can be written as a sum of positive squares in 8 ways, for example, as 2920681 + 18130564 = 1709^2 + 4258^2 .

It is not a de Polignac number, because 21051245 - 2² = 21051241 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051241) 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 in 15 ways as a sum of consecutive naturals, for example, 4175 + ... + 7715.

It is an arithmetic number, because the mean of its divisors is an integer number (1673595).

Almost surely, 2^21051245 is an apocalyptic number.

It is an amenable number.

21051245 is a deficient number, since it is larger than the sum of its proper divisors (5726275).

21051245 is a wasteful number, since it uses less digits than its factorization.

21051245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3616.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21051245 is about 4588.1635759855. The cubic root of 21051245 is about 276.1166497396.

Adding to 21051245 its reverse (54215012), we get a palindrome (75266257).

The spelling of 21051245 in words is "twenty-one million, fifty-one thousand, two hundred forty-five".