77681520 has 120 divisors (see below), whose sum is σ = 298168416. Its totient is φ = 17754624.

The previous prime is 77681507. The next prime is 77681543. The reversal of 77681520 is 2518677.

77681520 is a `hidden beast` number, since 77 + 68 + 1 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2667 + ... + 12746.

Almost surely, 2^77681520 is an apocalyptic number.

77681520 is a gapful number since it is divisible by the number (70) 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 77681520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149084208).

77681520 is an abundant number, since it is smaller than the sum of its proper divisors (220486896).

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

77681520 is a wasteful number, since it uses less digits than its factorization.

77681520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15439 (or 15430 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 77681520 is about 8813.7120443091. The cubic root of 77681520 is about 426.6835551041.

The spelling of 77681520 in words is "seventy-seven million, six hundred eighty-one thousand, five hundred twenty".