81243649 has 8 divisors (see below), whose sum is σ = 82944000. Its totient is φ = 79554192.

The previous prime is 81243607. The next prime is 81243661. The reversal of 81243649 is 94634218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81243649 - 2¹⁵ = 81210881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81241649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13312 + ... + 18430.

It is an arithmetic number, because the mean of its divisors is an integer number (10368000).

Almost surely, 2^81243649 is an apocalyptic number.

It is an amenable number.

81243649 is a deficient number, since it is larger than the sum of its proper divisors (1700351).

81243649 is a wasteful number, since it uses less digits than its factorization.

81243649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5447.

The product of its digits is 41472, while the sum is 37.

The square root of 81243649 is about 9013.5258916808. The cubic root of 81243649 is about 433.1082672799.

The spelling of 81243649 in words is "eighty-one million, two hundred forty-three thousand, six hundred forty-nine".