81721076 has 12 divisors (see below), whose sum is σ = 144822720. Its totient is φ = 40343160.

The previous prime is 81721051. The next prime is 81721103. The reversal of 81721076 is 67012718.

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, 128990 + ... + 129621.

It is an arithmetic number, because the mean of its divisors is an integer number (12068560).

Almost surely, 2^81721076 is an apocalyptic number.

It is an amenable number.

81721076 is a deficient number, since it is larger than the sum of its proper divisors (63101644).

81721076 is a wasteful number, since it uses less digits than its factorization.

81721076 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 258694 (or 258692 counting only the distinct ones).

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

The square root of 81721076 is about 9039.9710176527. The cubic root of 81721076 is about 433.9549954395.

The spelling of 81721076 in words is "eighty-one million, seven hundred twenty-one thousand, seventy-six".