1221385761 has 6 divisors (see below), whose sum is σ = 1764223890. Its totient is φ = 814257168.

The previous prime is 1221385747. The next prime is 1221385769. The reversal of 1221385761 is 1675831221.

It can be written as a sum of positive squares in only one way, i.e., 835499025 + 385886736 = 28905^2 + 19644^2 .

It is not a de Polignac number, because 1221385761 - 2¹⁷ = 1221254689 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1221385769) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 67854756 + ... + 67854773.

It is an arithmetic number, because the mean of its divisors is an integer number (294037315).

Almost surely, 2^1221385761 is an apocalyptic number.

It is an amenable number.

1221385761 is a deficient number, since it is larger than the sum of its proper divisors (542838129).

1221385761 is a wasteful number, since it uses less digits than its factorization.

1221385761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135709535 (or 135709532 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 1221385761 is about 34948.3298742587. The cubic root of 1221385761 is about 1068.9341472372.

The spelling of 1221385761 in words is "one billion, two hundred twenty-one million, three hundred eighty-five thousand, seven hundred sixty-one".