81619965 has 96 divisors (see below), whose sum is σ = 170726400. Its totient is φ = 35292672.

The previous prime is 81619961. The next prime is 81619969. The reversal of 81619965 is 56991618.

It is an interprime number because it is at equal distance from previous prime (81619961) and next prime (81619969).

It is not a de Polignac number, because 81619965 - 2² = 81619961 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81619965.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81619961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 547711 + ... + 547859.

It is an arithmetic number, because the mean of its divisors is an integer number (1778400).

Almost surely, 2^81619965 is an apocalyptic number.

It is an amenable number.

81619965 is an abundant number, since it is smaller than the sum of its proper divisors (89106435).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81619965 is a wasteful number, since it uses less digits than its factorization.

81619965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251 (or 248 counting only the distinct ones).

The product of its digits is 116640, while the sum is 45.

The square root of 81619965 is about 9034.3768462468. The cubic root of 81619965 is about 433.7759484735.

The spelling of 81619965 in words is "eighty-one million, six hundred nineteen thousand, nine hundred sixty-five".