1221605541 has 24 divisors (see below), whose sum is σ = 1965807480. Its totient is φ = 725832576.

The previous prime is 1221605521. The next prime is 1221605549. The reversal of 1221605541 is 1455061221.

1221605541 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 605 + 54 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 172817316 + 1048788225 = 13146^2 + 32385^2 .

It is not a de Polignac number, because 1221605541 - 2⁶ = 1221605477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221605549) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 176626 + ... + 183411.

It is an arithmetic number, because the mean of its divisors is an integer number (81908645).

Almost surely, 2^1221605541 is an apocalyptic number.

It is an amenable number.

1221605541 is a deficient number, since it is larger than the sum of its proper divisors (744201939).

1221605541 is a wasteful number, since it uses less digits than its factorization.

1221605541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360085 (or 360082 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

The square root of 1221605541 is about 34951.4740890853. The cubic root of 1221605541 is about 1068.9982591841.

Adding to 1221605541 its reverse (1455061221), we get a palindrome (2676666762).

The spelling of 1221605541 in words is "one billion, two hundred twenty-one million, six hundred five thousand, five hundred forty-one".