81721464 has 96 divisors (see below), whose sum is σ = 227525760. Its totient is φ = 24439360.

The previous prime is 81721439. The next prime is 81721469. The reversal of 81721464 is 46412718.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81721469) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 310597 + ... + 310859.

It is an arithmetic number, because the mean of its divisors is an integer number (2370060).

Almost surely, 2^81721464 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81721464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113762880).

81721464 is an abundant number, since it is smaller than the sum of its proper divisors (145804296).

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

81721464 is a wasteful number, since it uses less digits than its factorization.

81721464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 401 (or 386 counting only the distinct ones).

The product of its digits is 10752, while the sum is 33.

The square root of 81721464 is about 9039.9924778730. The cubic root of 81721464 is about 433.9556822239.

The spelling of 81721464 in words is "eighty-one million, seven hundred twenty-one thousand, four hundred sixty-four".