81244145664 has 768 divisors, whose sum is σ = 284320108800. Its totient is φ = 22932357120.

The previous prime is 81244145561. The next prime is 81244145699. The reversal of 81244145664 is 46654144218.

81244145664 is a `hidden beast` number, since 8 + 124 + 414 + 56 + 64 = 666.

It is a tau number, because it is divible by the number of its divisors (768).

It is a super-2 number, since 2×81244145664² (a number of 23 digits) contains 22 as substring.

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 63 ways as a sum of consecutive naturals, for example, 837568464 + ... + 837568560.

It is an arithmetic number, because the mean of its divisors is an integer number (370208475).

Almost surely, 2^81244145664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81244145664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142160054400).

81244145664 is an abundant number, since it is smaller than the sum of its proper divisors (203075963136).

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

81244145664 is an equidigital number, since it uses as much as digits as its factorization.

81244145664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168 (or 130 counting only the distinct ones).

The product of its digits is 737280, while the sum is 45.

The spelling of 81244145664 in words is "eighty-one billion, two hundred forty-four million, one hundred forty-five thousand, six hundred sixty-four".