21631061 has 2 divisors, whose sum is σ = 21631062. Its totient is φ = 21631060.

The previous prime is 21631039. The next prime is 21631081. The reversal of 21631061 is 16013612.

It is an a-pointer prime, because the next prime (21631081) can be obtained adding 21631061 to its sum of digits (20).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21446161 + 184900 = 4631^2 + 430^2 .

It is a cyclic number.

It is not a de Polignac number, because 21631061 - 2⁶ = 21630997 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21631081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10815530 + 10815531.

It is an arithmetic number, because the mean of its divisors is an integer number (10815531).

Almost surely, 2^21631061 is an apocalyptic number.

It is an amenable number.

21631061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21631061 is an equidigital number, since it uses as much as digits as its factorization.

21631061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21631061 is about 4650.9204465353. The cubic root of 21631061 is about 278.6287590342.

Adding to 21631061 its reverse (16013612), we get a palindrome (37644673).

The spelling of 21631061 in words is "twenty-one million, six hundred thirty-one thousand, sixty-one".