21120661 has 2 divisors, whose sum is σ = 21120662. Its totient is φ = 21120660.

The previous prime is 21120637. The next prime is 21120667. The reversal of 21120661 is 16602112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11628100 + 9492561 = 3410^2 + 3081^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120661 - 2⁵ = 21120629 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21120667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560330 + 10560331.

It is an arithmetic number, because the mean of its divisors is an integer number (10560331).

Almost surely, 2^21120661 is an apocalyptic number.

It is an amenable number.

21120661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120661 is an equidigital number, since it uses as much as digits as its factorization.

21120661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21120661 is about 4595.7220324994. The cubic root of 21120661 is about 276.4198128760.

Adding to 21120661 its reverse (16602112), we get a palindrome (37722773).

The spelling of 21120661 in words is "twenty-one million, one hundred twenty thousand, six hundred sixty-one".