21607121 has 2 divisors, whose sum is σ = 21607122. Its totient is φ = 21607120.

The previous prime is 21607111. The next prime is 21607127. The reversal of 21607121 is 12170612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19536400 + 2070721 = 4420^2 + 1439^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21607121 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21607093 and 21607102.

It is not a weakly prime, because it can be changed into another prime (21607127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10803560 + 10803561.

It is an arithmetic number, because the mean of its divisors is an integer number (10803561).

Almost surely, 2^21607121 is an apocalyptic number.

It is an amenable number.

21607121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21607121 is an equidigital number, since it uses as much as digits as its factorization.

21607121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 21607121 is about 4648.3460499408. The cubic root of 21607121 is about 278.5259310561.

Adding to 21607121 its reverse (12170612), we get a palindrome (33777733).

The spelling of 21607121 in words is "twenty-one million, six hundred seven thousand, one hundred twenty-one".