21611617 has 2 divisors, whose sum is σ = 21611618. Its totient is φ = 21611616.

The previous prime is 21611609. The next prime is 21611621. The reversal of 21611617 is 71611612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13905441 + 7706176 = 3729^2 + 2776^2 .

It is a cyclic number.

It is not a de Polignac number, because 21611617 - 2³ = 21611609 is a prime.

It is equal to p_1366216 and since 21611617 and 1366216 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21611591 and 21611600.

It is not a weakly prime, because it can be changed into another prime (21611687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10805808 + 10805809.

It is an arithmetic number, because the mean of its divisors is an integer number (10805809).

Almost surely, 2^21611617 is an apocalyptic number.

It is an amenable number.

21611617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21611617 is an equidigital number, since it uses as much as digits as its factorization.

21611617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 504, while the sum is 25.

The square root of 21611617 is about 4648.8296376615. The cubic root of 21611617 is about 278.5452482331.

The spelling of 21611617 in words is "twenty-one million, six hundred eleven thousand, six hundred seventeen".