81601919 has 4 divisors (see below), whose sum is σ = 93259344. Its totient is φ = 69944496.

The previous prime is 81601901. The next prime is 81601937. The reversal of 81601919 is 91910618.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (81601901) and next prime (81601937).

It is a cyclic number.

It is not a de Polignac number, because 81601919 - 2¹² = 81597823 is a prime.

It is a super-2 number, since 2×81601919² = 13317746368965122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81601939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5828702 + ... + 5828715.

It is an arithmetic number, because the mean of its divisors is an integer number (23314836).

Almost surely, 2^81601919 is an apocalyptic number.

81601919 is a deficient number, since it is larger than the sum of its proper divisors (11657425).

81601919 is a wasteful number, since it uses less digits than its factorization.

81601919 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11657424.

The product of its (nonzero) digits is 3888, while the sum is 35.

The square root of 81601919 is about 9033.3780503198. The cubic root of 81601919 is about 433.7439771384.

The spelling of 81601919 in words is "eighty-one million, six hundred one thousand, nine hundred nineteen".