21696121 has 2 divisors, whose sum is σ = 21696122. Its totient is φ = 21696120.

The previous prime is 21696083. The next prime is 21696127. The reversal of 21696121 is 12169612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19900521 + 1795600 = 4461^2 + 1340^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21696121 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 21696121.

It is not a weakly prime, because it can be changed into another prime (21696127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10848060 + 10848061.

It is an arithmetic number, because the mean of its divisors is an integer number (10848061).

Almost surely, 2^21696121 is an apocalyptic number.

It is an amenable number.

21696121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21696121 is an equidigital number, since it uses as much as digits as its factorization.

21696121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 28.

The square root of 21696121 is about 4657.9095096406. The cubic root of 21696121 is about 278.9078244514.

The spelling of 21696121 in words is "twenty-one million, six hundred ninety-six thousand, one hundred twenty-one".