81321224 has 8 divisors (see below), whose sum is σ = 152477310. Its totient is φ = 40660608.

The previous prime is 81321223. The next prime is 81321269. The reversal of 81321224 is 42212318.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 47472100 + 33849124 = 6890^2 + 5818^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×81321224² = 13226282945716352, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81321224.

It is not an unprimeable number, because it can be changed into a prime (81321223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5082569 + ... + 5082584.

Almost surely, 2^81321224 is an apocalyptic number.

It is an amenable number.

81321224 is a deficient number, since it is larger than the sum of its proper divisors (71156086).

81321224 is a wasteful number, since it uses less digits than its factorization.

81321224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10165159 (or 10165155 counting only the distinct ones).

The product of its digits is 768, while the sum is 23.

The square root of 81321224 is about 9017.8281198967. The cubic root of 81321224 is about 433.2460736856.

The spelling of 81321224 in words is "eighty-one million, three hundred twenty-one thousand, two hundred twenty-four".