81631216 has 20 divisors (see below), whose sum is σ = 158335600. Its totient is φ = 40770432.

The previous prime is 81631211. The next prime is 81631217. The reversal of 81631216 is 61213618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81631211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15805 + ... + 20323.

It is an arithmetic number, because the mean of its divisors is an integer number (7916780).

Almost surely, 2^81631216 is an apocalyptic number.

It is an amenable number.

81631216 is a deficient number, since it is larger than the sum of its proper divisors (76704384).

81631216 is a wasteful number, since it uses less digits than its factorization.

81631216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5656 (or 5650 counting only the distinct ones).

The product of its digits is 1728, while the sum is 28.

The square root of 81631216 is about 9034.9995019369. Note that the first 3 decimals coincide. The cubic root of 81631216 is about 433.7958790096.

The spelling of 81631216 in words is "eighty-one million, six hundred thirty-one thousand, two hundred sixteen".