81314721 has 6 divisors (see below), whose sum is σ = 117454610. Its totient is φ = 54209808.

The previous prime is 81314719. The next prime is 81314749. The reversal of 81314721 is 12741318.

It can be written as a sum of positive squares in only one way, i.e., 81000000 + 314721 = 9000^2 + 561^2 .

It is not a de Polignac number, because 81314721 - 2¹ = 81314719 is a prime.

It is a super-2 number, since 2×81314721² = 13224167702615682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81314711) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4517476 + ... + 4517493.

Almost surely, 2^81314721 is an apocalyptic number.

It is an amenable number.

81314721 is a deficient number, since it is larger than the sum of its proper divisors (36139889).

81314721 is a wasteful number, since it uses less digits than its factorization.

81314721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9034975 (or 9034972 counting only the distinct ones).

The product of its digits is 1344, while the sum is 27.

The square root of 81314721 is about 9017.4675491515. The cubic root of 81314721 is about 433.2345249403.

It can be divided in two parts, 81 and 314721, that multiplied together give a square (25492401 = 5049²).

The spelling of 81314721 in words is "eighty-one million, three hundred fourteen thousand, seven hundred twenty-one".