21025513 has 2 divisors, whose sum is σ = 21025514. Its totient is φ = 21025512.

The previous prime is 21025507. The next prime is 21025561. The reversal of 21025513 is 31552012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20502784 + 522729 = 4528^2 + 723^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21025513 is a prime.

It is not a weakly prime, because it can be changed into another prime (21025313) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10512756 + 10512757.

It is an arithmetic number, because the mean of its divisors is an integer number (10512757).

Almost surely, 2^21025513 is an apocalyptic number.

It is an amenable number.

21025513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21025513 is an equidigital number, since it uses as much as digits as its factorization.

21025513 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21025513 is about 4585.3585465043. The cubic root of 21025513 is about 276.0041000931.

Adding to 21025513 its reverse (31552012), we get a palindrome (52577525).

The spelling of 21025513 in words is "twenty-one million, twenty-five thousand, five hundred thirteen".