1220775721 has 4 divisors (see below), whose sum is σ = 1331755344. Its totient is φ = 1109796100.

The previous prime is 1220775713. The next prime is 1220775739. The reversal of 1220775721 is 1275770221.

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 1220775721 - 2³ = 1220775713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1220775781) 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, 55489795 + ... + 55489816.

It is an arithmetic number, because the mean of its divisors is an integer number (332938836).

Almost surely, 2^1220775721 is an apocalyptic number.

1220775721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1220775721 is a deficient number, since it is larger than the sum of its proper divisors (110979623).

1220775721 is a wasteful number, since it uses less digits than its factorization.

1220775721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110979622.

The product of its (nonzero) digits is 13720, while the sum is 34.

The square root of 1220775721 is about 34939.6010423702. The cubic root of 1220775721 is about 1068.7561523716.

The spelling of 1220775721 in words is "one billion, two hundred twenty million, seven hundred seventy-five thousand, seven hundred twenty-one".