21015461 has 2 divisors, whose sum is σ = 21015462. Its totient is φ = 21015460.

The previous prime is 21015437. The next prime is 21015473. The reversal of 21015461 is 16451012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18105025 + 2910436 = 4255^2 + 1706^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21015461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21015061) 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, 10507730 + 10507731.

It is an arithmetic number, because the mean of its divisors is an integer number (10507731).

Almost surely, 2^21015461 is an apocalyptic number.

It is an amenable number.

21015461 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015461 is an equidigital number, since it uses as much as digits as its factorization.

21015461 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21015461 is about 4584.2623179744. The cubic root of 21015461 is about 275.9601085313.

Adding to 21015461 its reverse (16451012), we get a palindrome (37466473).

The spelling of 21015461 in words is "twenty-one million, fifteen thousand, four hundred sixty-one".