81651987 has 12 divisors (see below), whose sum is σ = 124149480. Its totient is φ = 51569568.

The previous prime is 81651979. The next prime is 81652049. The reversal of 81651987 is 78915618.

It is not a de Polignac number, because 81651987 - 2³ = 81651979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81601987) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 238578 + ... + 238919.

It is an arithmetic number, because the mean of its divisors is an integer number (10345790).

Almost surely, 2^81651987 is an apocalyptic number.

81651987 is a deficient number, since it is larger than the sum of its proper divisors (42497493).

81651987 is a wasteful number, since it uses less digits than its factorization.

81651987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 477522 (or 477519 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 81651987 is about 9036.1489031556. The cubic root of 81651987 is about 433.8326688984.

The spelling of 81651987 in words is "eighty-one million, six hundred fifty-one thousand, nine hundred eighty-seven".