771221561 has 4 divisors (see below), whose sum is σ = 841332624. Its totient is φ = 701110500.

The previous prime is 771221551. The next prime is 771221569. The reversal of 771221561 is 165122177.

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-771221561 is a prime.

It is not an unprimeable number, because it can be changed into a prime (771221569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35055515 + ... + 35055536.

It is an arithmetic number, because the mean of its divisors is an integer number (210333156).

Almost surely, 2^771221561 is an apocalyptic number.

It is an amenable number.

771221561 is a deficient number, since it is larger than the sum of its proper divisors (70111063).

771221561 is a wasteful number, since it uses less digits than its factorization.

771221561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70111062.

The product of its digits is 5880, while the sum is 32.

The square root of 771221561 is about 27770.8761294994. The cubic root of 771221561 is about 917.0500823532.

The spelling of 771221561 in words is "seven hundred seventy-one million, two hundred twenty-one thousand, five hundred sixty-one".