81145720 has 16 divisors (see below), whose sum is σ = 182577960. Its totient is φ = 32458272.

The previous prime is 81145717. The next prime is 81145721. The reversal of 81145720 is 2754118.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81145721) 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, 1014282 + ... + 1014361.

Almost surely, 2^81145720 is an apocalyptic number.

It is an amenable number.

81145720 is an abundant number, since it is smaller than the sum of its proper divisors (101432240).

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

81145720 is a wasteful number, since it uses less digits than its factorization.

81145720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2028654 (or 2028650 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 81145720 is about 9008.0919178259. The cubic root of 81145720 is about 432.9341781337.

Adding to 81145720 its reverse (2754118), we get a palindrome (83899838).

The spelling of 81145720 in words is "eighty-one million, one hundred forty-five thousand, seven hundred twenty".