81203920 has 40 divisors (see below), whose sum is σ = 215771904. Its totient is φ = 27841152.

The previous prime is 81203851. The next prime is 81203953. The reversal of 81203920 is 2930218.

It is a tau number, because it is divible by the number of its divisors (40).

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, 71944 + ... + 73063.

Almost surely, 2^81203920 is an apocalyptic number.

81203920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81203920 is an abundant number, since it is smaller than the sum of its proper divisors (134567984).

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

81203920 is a wasteful number, since it uses less digits than its factorization.

81203920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145027 (or 145021 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 81203920 is about 9011.3217676432. The cubic root of 81203920 is about 433.0376576010.

The spelling of 81203920 in words is "eighty-one million, two hundred three thousand, nine hundred twenty".