71521961 has 4 divisors (see below), whose sum is σ = 81739392. Its totient is φ = 61304532.

The previous prime is 71521949. The next prime is 71521979. The reversal of 71521961 is 16912517.

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 a de Polignac number, because none of the positive numbers 2^k-71521961 is a prime.

It is not an unprimeable number, because it can be changed into a prime (71521661) 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, 5108705 + ... + 5108718.

It is an arithmetic number, because the mean of its divisors is an integer number (20434848).

Almost surely, 2^71521961 is an apocalyptic number.

It is an amenable number.

71521961 is a deficient number, since it is larger than the sum of its proper divisors (10217431).

71521961 is a wasteful number, since it uses less digits than its factorization.

71521961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10217430.

The product of its digits is 3780, while the sum is 32.

The square root of 71521961 is about 8457.0657440982. The cubic root of 71521961 is about 415.0940146029.

The spelling of 71521961 in words is "seventy-one million, five hundred twenty-one thousand, nine hundred sixty-one".