81153481 has 2 divisors, whose sum is σ = 81153482.
Its totient is φ = 81153480.
The previous prime is 81153439. The next prime is 81153509. The reversal of 81153481 is 18435118.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 79923600 + 1229881 = 8940^2 + 1109^2
It is a cyclic number.
It is not a de Polignac number, because 81153481 - 27 = 81153353 is a prime.
It is a super-2 number, since 2×811534812 = 13171774956834722, which contains 22 as substring.
It is not a weakly prime, because it can be changed into another prime (81153431) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40576740 + 40576741.
It is an arithmetic number, because the mean of its divisors is an integer number (40576741).
Almost surely, 281153481 is an apocalyptic number.
It is an amenable number.
81153481 is a deficient number, since it is larger than the sum of its proper divisors (1).
81153481 is an equidigital number, since it uses as much as digits as its factorization.
81153481 is an evil number, because the sum of its binary digits is even.
The product of its digits is 3840, while the sum is 31.
The square root of 81153481 is about 9008.5226868782.
The cubic root of 81153481 is about 432.9479800325.
Adding to 81153481 its reverse (18435118), we get a palindrome (99588599).
The spelling of 81153481 in words is "eighty-one million, one hundred fifty-three thousand, four hundred eighty-one".