81429840 has 80 divisors (see below), whose sum is σ = 280488000. Its totient is φ = 21714048.

The previous prime is 81429827. The next prime is 81429893. The reversal of 81429840 is 4892418.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81429795 and 81429804.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16690 + ... + 21009.

It is an arithmetic number, because the mean of its divisors is an integer number (3506100).

Almost surely, 2^81429840 is an apocalyptic number.

81429840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81429840 is an abundant number, since it is smaller than the sum of its proper divisors (199058160).

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

81429840 is a wasteful number, since it uses less digits than its factorization.

81429840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37721 (or 37709 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 81429840 is about 9023.8484029820. The cubic root of 81429840 is about 433.4388750156.

The spelling of 81429840 in words is "eighty-one million, four hundred twenty-nine thousand, eight hundred forty".