81720412 has 12 divisors (see below), whose sum is σ = 143556336. Its totient is φ = 40704320.

The previous prime is 81720409. The next prime is 81720427. The reversal of 81720412 is 21402718.

It is a happy number.

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, 37789 + ... + 39892.

It is an arithmetic number, because the mean of its divisors is an integer number (11963028).

Almost surely, 2^81720412 is an apocalyptic number.

It is an amenable number.

81720412 is a deficient number, since it is larger than the sum of its proper divisors (61835924).

81720412 is a wasteful number, since it uses less digits than its factorization.

81720412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77948 (or 77946 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 81720412 is about 9039.9342917966. The cubic root of 81720412 is about 433.9538201128.

It can be divided in two parts, 817204 and 12, that added together give a square (817216 = 904²).

The spelling of 81720412 in words is "eighty-one million, seven hundred twenty thousand, four hundred twelve".