81553639 has 8 divisors (see below), whose sum is σ = 82150848. Its totient is φ = 80959200.

The previous prime is 81553621. The next prime is 81553651. The reversal of 81553639 is 93635518.

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 81553639 - 2⁹ = 81553127 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81553139) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 115989 + ... + 116689.

It is an arithmetic number, because the mean of its divisors is an integer number (10268856).

Almost surely, 2^81553639 is an apocalyptic number.

81553639 is a deficient number, since it is larger than the sum of its proper divisors (597209).

81553639 is a wasteful number, since it uses less digits than its factorization.

81553639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1385.

The product of its digits is 97200, while the sum is 40.

The square root of 81553639 is about 9030.7053434380. The cubic root of 81553639 is about 433.6584183232.

The spelling of 81553639 in words is "eighty-one million, five hundred fifty-three thousand, six hundred thirty-nine".