81638880 has 48 divisors (see below), whose sum is σ = 257163984. Its totient is φ = 21770240.

The previous prime is 81638867. The next prime is 81638881. The reversal of 81638880 is 8883618.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81638881) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 84561 + ... + 85520.

It is an arithmetic number, because the mean of its divisors is an integer number (5357583).

Almost surely, 2^81638880 is an apocalyptic number.

81638880 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81638880 is an abundant number, since it is smaller than the sum of its proper divisors (175525104).

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

81638880 is a wasteful number, since it uses less digits than its factorization.

81638880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170099 (or 170091 counting only the distinct ones).

The product of its (nonzero) digits is 73728, while the sum is 42.

The square root of 81638880 is about 9035.4236203954. The cubic root of 81638880 is about 433.8094543212.

The spelling of 81638880 in words is "eighty-one million, six hundred thirty-eight thousand, eight hundred eighty".