81761720 has 16 divisors (see below), whose sum is σ = 183963960. Its totient is φ = 32704672.

The previous prime is 81761699. The next prime is 81761767. The reversal of 81761720 is 2716718.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1021982 + ... + 1022061.

Almost surely, 2^81761720 is an apocalyptic number.

It is an amenable number.

81761720 is an abundant number, since it is smaller than the sum of its proper divisors (102202240).

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

81761720 is a wasteful number, since it uses less digits than its factorization.

81761720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2044054 (or 2044050 counting only the distinct ones).

The product of its (nonzero) digits is 4704, while the sum is 32.

The square root of 81761720 is about 9042.2187542660. The cubic root of 81761720 is about 434.0269260620.

The spelling of 81761720 in words is "eighty-one million, seven hundred sixty-one thousand, seven hundred twenty".