81617505619 has 4 divisors (see below), whose sum is σ = 87895775296. Its totient is φ = 75339235944.

The previous prime is 81617505587. The next prime is 81617505659. The reversal of 81617505619 is 91650571618.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81617505619 - 2⁵ = 81617505587 is a prime.

It is a super-2 number, since 2×81617505619² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81617505659) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3139134819 + ... + 3139134844.

It is an arithmetic number, because the mean of its divisors is an integer number (21973943824).

Almost surely, 2^81617505619 is an apocalyptic number.

81617505619 is a deficient number, since it is larger than the sum of its proper divisors (6278269677).

81617505619 is a wasteful number, since it uses less digits than its factorization.

81617505619 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6278269676.

The product of its (nonzero) digits is 453600, while the sum is 49.

The spelling of 81617505619 in words is "eighty-one billion, six hundred seventeen million, five hundred five thousand, six hundred nineteen".