21103961 has 2 divisors, whose sum is σ = 21103962. Its totient is φ = 21103960.

The previous prime is 21103937. The next prime is 21104011. The reversal of 21103961 is 16930112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18318400 + 2785561 = 4280^2 + 1669^2 .

It is a cyclic number.

It is not a de Polignac number, because 21103961 - 2⁶ = 21103897 is a prime.

It is not a weakly prime, because it can be changed into another prime (21106961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551980 + 10551981.

It is an arithmetic number, because the mean of its divisors is an integer number (10551981).

Almost surely, 2^21103961 is an apocalyptic number.

It is an amenable number.

21103961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21103961 is an equidigital number, since it uses as much as digits as its factorization.

21103961 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 21103961 is about 4593.9047661004. The cubic root of 21103961 is about 276.3469390823.

Subtracting from 21103961 its reverse (16930112), we obtain a square (4173849 = 2043²).

The spelling of 21103961 in words is "twenty-one million, one hundred three thousand, nine hundred sixty-one".