21038561 has 2 divisors, whose sum is σ = 21038562. Its totient is φ = 21038560.

The previous prime is 21038557. The next prime is 21038579. The reversal of 21038561 is 16583012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20647936 + 390625 = 4544^2 + 625^2 .

It is a cyclic number.

It is not a de Polignac number, because 21038561 - 2² = 21038557 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21038561.

It is not a weakly prime, because it can be changed into another prime (21038531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10519280 + 10519281.

It is an arithmetic number, because the mean of its divisors is an integer number (10519281).

Almost surely, 2^21038561 is an apocalyptic number.

It is an amenable number.

21038561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21038561 is an equidigital number, since it uses as much as digits as its factorization.

21038561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21038561 is about 4586.7811153357. The cubic root of 21038561 is about 276.0611824386.

The spelling of 21038561 in words is "twenty-one million, thirty-eight thousand, five hundred sixty-one".