81564388 has 24 divisors (see below), whose sum is σ = 145152000. Its totient is φ = 40098528.

The previous prime is 81564383. The next prime is 81564389. The reversal of 81564388 is 88346518.

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (81564383) 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 7 ways as a sum of consecutive naturals, for example, 63133 + ... + 64411.

It is an arithmetic number, because the mean of its divisors is an integer number (6048000).

Almost surely, 2^81564388 is an apocalyptic number.

It is an amenable number.

81564388 is a deficient number, since it is larger than the sum of its proper divisors (63587612).

81564388 is a wasteful number, since it uses less digits than its factorization.

81564388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1539 (or 1537 counting only the distinct ones).

The product of its digits is 184320, while the sum is 43.

The square root of 81564388 is about 9031.3004600666. The cubic root of 81564388 is about 433.6774699544.

It can be divided in two parts, 8156 and 4388, that added together give a square (12544 = 112²).

The spelling of 81564388 in words is "eighty-one million, five hundred sixty-four thousand, three hundred eighty-eight".