21411661 has 2 divisors, whose sum is σ = 21411662. Its totient is φ = 21411660.

The previous prime is 21411623. The next prime is 21411667. The reversal of 21411661 is 16611412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17589636 + 3822025 = 4194^2 + 1955^2 .

It is a cyclic number.

It is not a de Polignac number, because 21411661 - 2⁹ = 21411149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21411667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10705830 + 10705831.

It is an arithmetic number, because the mean of its divisors is an integer number (10705831).

Almost surely, 2^21411661 is an apocalyptic number.

It is an amenable number.

21411661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21411661 is an equidigital number, since it uses as much as digits as its factorization.

21411661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 22.

The square root of 21411661 is about 4627.2736033219. The cubic root of 21411661 is about 277.6835287304.

The spelling of 21411661 in words is "twenty-one million, four hundred eleven thousand, six hundred sixty-one".