21015161 has 2 divisors, whose sum is σ = 21015162. Its totient is φ = 21015160.

The previous prime is 21015143. The next prime is 21015199. The reversal of 21015161 is 16151012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17480761 + 3534400 = 4181^2 + 1880^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015161 - 2⁶ = 21015097 is a prime.

It is a Chen prime.

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, 10507580 + 10507581.

It is an arithmetic number, because the mean of its divisors is an integer number (10507581).

Almost surely, 2^21015161 is an apocalyptic number.

It is an amenable number.

21015161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015161 is an equidigital number, since it uses as much as digits as its factorization.

21015161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60, while the sum is 17.

The square root of 21015161 is about 4584.2295972170. The cubic root of 21015161 is about 275.9587953961.

Adding to 21015161 its reverse (16151012), we get a palindrome (37166173).

The spelling of 21015161 in words is "twenty-one million, fifteen thousand, one hundred sixty-one".