81945515 has 8 divisors (see below), whose sum is σ = 99579840. Its totient is φ = 64726272.

The previous prime is 81945469. The next prime is 81945517. The reversal of 81945515 is 51554918.

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 81945515 - 2¹⁶ = 81879979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81945517) 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, 103334 + ... + 104123.

It is an arithmetic number, because the mean of its divisors is an integer number (12447480).

Almost surely, 2^81945515 is an apocalyptic number.

81945515 is a deficient number, since it is larger than the sum of its proper divisors (17634325).

81945515 is a wasteful number, since it uses less digits than its factorization.

81945515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 207541.

The product of its digits is 36000, while the sum is 38.

The square root of 81945515 is about 9052.3762073833. The cubic root of 81945515 is about 434.3519040564.

The spelling of 81945515 in words is "eighty-one million, nine hundred forty-five thousand, five hundred fifteen".