81471557 has 2 divisors, whose sum is σ = 81471558. Its totient is φ = 81471556.

The previous prime is 81471553. The next prime is 81471581. The reversal of 81471557 is 75517418.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 47761921 + 33709636 = 6911^2 + 5806^2 .

It is a cyclic number.

It is not a de Polignac number, because 81471557 - 2² = 81471553 is a prime.

It is a super-2 number, since 2×81471557² = 13275229200008498, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81471557.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81471553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40735778 + 40735779.

It is an arithmetic number, because the mean of its divisors is an integer number (40735779).

Almost surely, 2^81471557 is an apocalyptic number.

It is an amenable number.

81471557 is a deficient number, since it is larger than the sum of its proper divisors (1).

81471557 is an equidigital number, since it uses as much as digits as its factorization.

81471557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 39200, while the sum is 38.

The square root of 81471557 is about 9026.1595930938. The cubic root of 81471557 is about 433.5128801659.

It can be divided in two parts, 81471 and 557, that added together give a palindrome (82028).

The spelling of 81471557 in words is "eighty-one million, four hundred seventy-one thousand, five hundred fifty-seven".