81878417 has 4 divisors (see below), whose sum is σ = 81924276. Its totient is φ = 81832560.

The previous prime is 81878393. The next prime is 81878441. The reversal of 81878417 is 71487818.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (81878393) and next prime (81878441).

It can be written as a sum of positive squares in 2 ways, for example, as 5909761 + 75968656 = 2431^2 + 8716^2 .

It is a cyclic number.

It is not a de Polignac number, because 81878417 - 2¹² = 81874321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81878117) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20138 + ... + 23859.

It is an arithmetic number, because the mean of its divisors is an integer number (20481069).

Almost surely, 2^81878417 is an apocalyptic number.

It is an amenable number.

81878417 is a deficient number, since it is larger than the sum of its proper divisors (45859).

81878417 is a wasteful number, since it uses less digits than its factorization.

81878417 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45858.

The product of its digits is 100352, while the sum is 44.

The square root of 81878417 is about 9048.6693496889. The cubic root of 81878417 is about 434.2333207831.

The spelling of 81878417 in words is "eighty-one million, eight hundred seventy-eight thousand, four hundred seventeen".