81669149 has 2 divisors, whose sum is σ = 81669150. Its totient is φ = 81669148.

The previous prime is 81669121. The next prime is 81669151. The reversal of 81669149 is 94196618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 75568249 + 6100900 = 8693^2 + 2470^2 .

It is a cyclic number.

It is not a de Polignac number, because 81669149 - 2⁸ = 81668893 is a prime.

It is a Sophie Germain prime.

Together with 81669151, it forms a pair of twin primes.

It is a Chen 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 (81669109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40834574 + 40834575.

It is an arithmetic number, because the mean of its divisors is an integer number (40834575).

Almost surely, 2^81669149 is an apocalyptic number.

It is an amenable number.

81669149 is a deficient number, since it is larger than the sum of its proper divisors (1).

81669149 is an equidigital number, since it uses as much as digits as its factorization.

81669149 is an evil number, because the sum of its binary digits is even.

The product of its digits is 93312, while the sum is 44.

The square root of 81669149 is about 9037.0984834736. The cubic root of 81669149 is about 433.8630617684.

It can be divided in two parts, 81669 and 149, that added together give a palindrome (81818).

The spelling of 81669149 in words is "eighty-one million, six hundred sixty-nine thousand, one hundred forty-nine".