81709689600 has 2160 divisors, whose sum is σ = 397459560960. Its totient is φ = 16057958400.

The previous prime is 81709689599. The next prime is 81709689647. The reversal of 81709689600 is 698690718.

It is a tau number, because it is divible by the number of its divisors (2160).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 918086356 + ... + 918086444.

It is an arithmetic number, because the mean of its divisors is an integer number (184009056).

Almost surely, 2^81709689600 is an apocalyptic number.

81709689600 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81709689600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (198729780480).

81709689600 is an abundant number, since it is smaller than the sum of its proper divisors (315749871360).

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

81709689600 is a wasteful number, since it uses less digits than its factorization.

81709689600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168 (or 140 counting only the distinct ones).

The product of its (nonzero) digits is 1306368, while the sum is 54.

It can be divided in two parts, 81 and 709689600, that multiplied together give a square (57484857600 = 239760²).

The spelling of 81709689600 in words is "eighty-one billion, seven hundred nine million, six hundred eighty-nine thousand, six hundred".