66561331 has 2 divisors, whose sum is σ = 66561332. Its totient is φ = 66561330.

The previous prime is 66561289. The next prime is 66561337. The reversal of 66561331 is 13316566.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66561331 - 2¹⁵ = 66528563 is a prime.

It is a super-2 number, since 2×66561331² = 8860821568983122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 66561293 and 66561302.

It is not a weakly prime, because it can be changed into another prime (66561337) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33280665 + 33280666.

It is an arithmetic number, because the mean of its divisors is an integer number (33280666).

Almost surely, 2^66561331 is an apocalyptic number.

66561331 is a deficient number, since it is larger than the sum of its proper divisors (1).

66561331 is an equidigital number, since it uses as much as digits as its factorization.

66561331 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9720, while the sum is 31.

The square root of 66561331 is about 8158.5127933956. The cubic root of 66561331 is about 405.2664628626.

Adding to 66561331 its reverse (13316566), we get a palindrome (79877897).

The spelling of 66561331 in words is "sixty-six million, five hundred sixty-one thousand, three hundred thirty-one".