21125761 has 2 divisors, whose sum is σ = 21125762. Its totient is φ = 21125760.

The previous prime is 21125749. The next prime is 21125789. The reversal of 21125761 is 16752112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20875761 + 250000 = 4569^2 + 500^2 .

It is a cyclic number.

It is not a de Polignac number, because 21125761 - 2⁵ = 21125729 is a prime.

It is not a weakly prime, because it can be changed into another prime (21125711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562880 + 10562881.

It is an arithmetic number, because the mean of its divisors is an integer number (10562881).

Almost surely, 2^21125761 is an apocalyptic number.

It is an amenable number.

21125761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21125761 is an equidigital number, since it uses as much as digits as its factorization.

21125761 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 840, while the sum is 25.

The square root of 21125761 is about 4596.2768628532. The cubic root of 21125761 is about 276.4420600899.

Adding to 21125761 its reverse (16752112), we get a palindrome (37877873).

It can be divided in two parts, 2 and 1125761, that multiplied together give a palindrome (2251522).

The spelling of 21125761 in words is "twenty-one million, one hundred twenty-five thousand, seven hundred sixty-one".