81166554 has 48 divisors (see below), whose sum is σ = 202151040. Its totient is φ = 23055840.

The previous prime is 81166549. The next prime is 81166559. The reversal of 81166554 is 45566118.

It is an interprime number because it is at equal distance from previous prime (81166549) and next prime (81166559).

It is not an unprimeable number, because it can be changed into a prime (81166559) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21027 + ... + 24585.

It is an arithmetic number, because the mean of its divisors is an integer number (4211480).

Almost surely, 2^81166554 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81166554, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101075520).

81166554 is an abundant number, since it is smaller than the sum of its proper divisors (120984486).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81166554 is a wasteful number, since it uses less digits than its factorization.

81166554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3755 (or 3752 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

The square root of 81166554 is about 9009.2482483279. The cubic root of 81166554 is about 432.9712266223.

The spelling of 81166554 in words is "eighty-one million, one hundred sixty-six thousand, five hundred fifty-four".