81619867520 has 64 divisors (see below), whose sum is σ = 197592523200. Its totient is φ = 32234661888.

The previous prime is 81619867513. The next prime is 81619867531. The reversal of 81619867520 is 2576891618.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 756599 + ... + 857718.

It is an arithmetic number, because the mean of its divisors is an integer number (3087383175).

Almost surely, 2^81619867520 is an apocalyptic number.

81619867520 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81619867520 is an abundant number, since it is smaller than the sum of its proper divisors (115972655680).

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

81619867520 is a wasteful number, since it uses less digits than its factorization.

81619867520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1614415 (or 1614403 counting only the distinct ones).

The product of its (nonzero) digits is 1451520, while the sum is 53.

The spelling of 81619867520 in words is "eighty-one billion, six hundred nineteen million, eight hundred sixty-seven thousand, five hundred twenty".