81766797840 has 1680 divisors, whose sum is σ = 373782076416. Its totient is φ = 16460236800.

The previous prime is 81766797823. The next prime is 81766797857. The reversal of 81766797840 is 4879766718.

It is an interprime number because it is at equal distance from previous prime (81766797823) and next prime (81766797857).

It is a tau number, because it is divible by the number of its divisors (1680).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 335 ways as a sum of consecutive naturals, for example, 1151645005 + ... + 1151645075.

Almost surely, 2^81766797840 is an apocalyptic number.

81766797840 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 81766797840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (186891038208).

81766797840 is an abundant number, since it is smaller than the sum of its proper divisors (292015278576).

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

81766797840 is a wasteful number, since it uses less digits than its factorization.

81766797840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160 (or 132 counting only the distinct ones).

The product of its (nonzero) digits is 28449792, while the sum is 63.

The spelling of 81766797840 in words is "eighty-one billion, seven hundred sixty-six million, seven hundred ninety-seven thousand, eight hundred forty".