81554640 has 40 divisors (see below), whose sum is σ = 252820128. Its totient is φ = 21747840.

The previous prime is 81554639. The next prime is 81554663. The reversal of 81554640 is 4645518.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 169666 + ... + 170145.

Almost surely, 2^81554640 is an apocalyptic number.

81554640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81554640 is an abundant number, since it is smaller than the sum of its proper divisors (171265488).

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

81554640 is a wasteful number, since it uses less digits than its factorization.

81554640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339827 (or 339821 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 33.

The square root of 81554640 is about 9030.7607652955. The cubic root of 81554640 is about 433.6601925759.

It can be divided in two parts, 815 and 54640, that added together give a palindrome (55455).

The spelling of 81554640 in words is "eighty-one million, five hundred fifty-four thousand, six hundred forty".