81553081 has 2 divisors, whose sum is σ = 81553082. Its totient is φ = 81553080.

The previous prime is 81553019. The next prime is 81553091. The reversal of 81553081 is 18035518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73685056 + 7868025 = 8584^2 + 2805^2 .

It is a cyclic number.

It is not a de Polignac number, because 81553081 - 2¹¹ = 81551033 is a prime.

It is a super-2 number, since 2×81553081² = 13301810041185122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81553091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40776540 + 40776541.

It is an arithmetic number, because the mean of its divisors is an integer number (40776541).

Almost surely, 2^81553081 is an apocalyptic number.

81553081 is the 5712-nd centered pentagonal number.

It is an amenable number.

81553081 is a deficient number, since it is larger than the sum of its proper divisors (1).

81553081 is an equidigital number, since it uses as much as digits as its factorization.

81553081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4800, while the sum is 31.

The square root of 81553081 is about 9030.6744487884. The cubic root of 81553081 is about 433.6574292729.

Adding to 81553081 its reverse (18035518), we get a palindrome (99588599).

It can be divided in two parts, 8155 and 3081, that added together give a square (11236 = 106²).

The spelling of 81553081 in words is "eighty-one million, five hundred fifty-three thousand, eighty-one".