1011221555 has 8 divisors (see below), whose sum is σ = 1225247712. Its totient is φ = 801122688.

The previous prime is 1011221551. The next prime is 1011221579. The reversal of 1011221555 is 5551221101.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1011221555 - 2² = 1011221551 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1011221555.

It is not an unprimeable number, because it can be changed into a prime (1011221551) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 981254 + ... + 982283.

It is an arithmetic number, because the mean of its divisors is an integer number (153155964).

Almost surely, 2^1011221555 is an apocalyptic number.

1011221555 is a deficient number, since it is larger than the sum of its proper divisors (214026157).

1011221555 is a wasteful number, since it uses less digits than its factorization.

1011221555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1963645.

The product of its (nonzero) digits is 500, while the sum is 23.

The square root of 1011221555 is about 31799.7099829542. The cubic root of 1011221555 is about 1003.7266134343.

Adding to 1011221555 its reverse (5551221101), we get a palindrome (6562442656).

The spelling of 1011221555 in words is "one billion, eleven million, two hundred twenty-one thousand, five hundred fifty-five".