81231740 has 24 divisors (see below), whose sum is σ = 171935232. Its totient is φ = 32235840.

The previous prime is 81231737. The next prime is 81231743. The reversal of 81231740 is 4713218.

It is an interprime number because it is at equal distance from previous prime (81231737) and next prime (81231743).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81231743) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13451 + ... + 18530.

It is an arithmetic number, because the mean of its divisors is an integer number (7163968).

Almost surely, 2^81231740 is an apocalyptic number.

It is an amenable number.

81231740 is an abundant number, since it is smaller than the sum of its proper divisors (90703492).

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

81231740 is a wasteful number, since it uses less digits than its factorization.

81231740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32117 (or 32115 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 81231740 is about 9012.8652491869. The cubic root of 81231740 is about 433.0871040322.

Adding to 81231740 its reverse (4713218), we get a palindrome (85944958).

The spelling of 81231740 in words is "eighty-one million, two hundred thirty-one thousand, seven hundred forty".