71520991 has 4 divisors (see below), whose sum is σ = 72426400. Its totient is φ = 70615584.

The previous prime is 71520973. The next prime is 71521001. The reversal of 71520991 is 19902517.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-71520991 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 (71520901) 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, 452586 + ... + 452743.

It is an arithmetic number, because the mean of its divisors is an integer number (18106600).

Almost surely, 2^71520991 is an apocalyptic number.

71520991 is a deficient number, since it is larger than the sum of its proper divisors (905409).

71520991 is an equidigital number, since it uses as much as digits as its factorization.

71520991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 905408.

The product of its (nonzero) digits is 5670, while the sum is 34.

The square root of 71520991 is about 8457.0083954079. The cubic root of 71520991 is about 415.0921380556.

The spelling of 71520991 in words is "seventy-one million, five hundred twenty thousand, nine hundred ninety-one".