81555547 has 2 divisors, whose sum is σ = 81555548. Its totient is φ = 81555546.

The previous prime is 81555533. The next prime is 81555557. The reversal of 81555547 is 74555518.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81555547 - 2¹⁹ = 81031259 is a prime.

It is not a weakly prime, because it can be changed into another prime (81555517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40777773 + 40777774.

It is an arithmetic number, because the mean of its divisors is an integer number (40777774).

Almost surely, 2^81555547 is an apocalyptic number.

81555547 is a deficient number, since it is larger than the sum of its proper divisors (1).

81555547 is an equidigital number, since it uses as much as digits as its factorization.

81555547 is an evil number, because the sum of its binary digits is even.

The product of its digits is 140000, while the sum is 40.

The square root of 81555547 is about 9030.8109824091. The cubic root of 81555547 is about 433.6618002030.

The spelling of 81555547 in words is "eighty-one million, five hundred fifty-five thousand, five hundred forty-seven".