78811531 has 4 divisors (see below), whose sum is σ = 81529200. Its totient is φ = 76093864.

The previous prime is 78811519. The next prime is 78811597. The reversal of 78811531 is 13511887.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13511887 = 3643 ⋅3709.

It is a cyclic number.

It is not a de Polignac number, because 78811531 - 2¹¹ = 78809483 is a prime.

It is a super-2 number, since 2×78811531² = 12422514837127922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78811231) 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, 1358791 + ... + 1358848.

It is an arithmetic number, because the mean of its divisors is an integer number (20382300).

Almost surely, 2^78811531 is an apocalyptic number.

78811531 is a deficient number, since it is larger than the sum of its proper divisors (2717669).

78811531 is a wasteful number, since it uses less digits than its factorization.

78811531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2717668.

The product of its digits is 6720, while the sum is 34.

The square root of 78811531 is about 8877.5858768023. The cubic root of 78811531 is about 428.7425514152.

The spelling of 78811531 in words is "seventy-eight million, eight hundred eleven thousand, five hundred thirty-one".