71815813 has 4 divisors (see below), whose sum is σ = 72081088. Its totient is φ = 71550540.

The previous prime is 71815781. The next prime is 71815817. The reversal of 71815813 is 31851817.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 71815813 - 2⁵ = 71815781 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71815817) 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, 132231 + ... + 132772.

It is an arithmetic number, because the mean of its divisors is an integer number (18020272).

Almost surely, 2^71815813 is an apocalyptic number.

It is an amenable number.

71815813 is a deficient number, since it is larger than the sum of its proper divisors (265275).

71815813 is a wasteful number, since it uses less digits than its factorization.

71815813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265274.

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

The square root of 71815813 is about 8474.4211011726. The cubic root of 71815813 is about 415.6617168686.

The spelling of 71815813 in words is "seventy-one million, eight hundred fifteen thousand, eight hundred thirteen".