1221016557 has 8 divisors (see below), whose sum is σ = 1628311360. Its totient is φ = 813866400.

The previous prime is 1221016553. The next prime is 1221016579. The reversal of 1221016557 is 7556101221.

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

It is not a de Polignac number, because 1221016557 - 2² = 1221016553 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221016553) 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, 14632 + ... + 51537.

It is an arithmetic number, because the mean of its divisors is an integer number (203538920).

Almost surely, 2^1221016557 is an apocalyptic number.

It is an amenable number.

1221016557 is a deficient number, since it is larger than the sum of its proper divisors (407294803).

1221016557 is an equidigital number, since it uses as much as digits as its factorization.

1221016557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72323.

The product of its (nonzero) digits is 4200, while the sum is 30.

The square root of 1221016557 is about 34943.0473341980. The cubic root of 1221016557 is about 1068.8264295535.

Adding to 1221016557 its reverse (7556101221), we get a palindrome (8777117778).

The spelling of 1221016557 in words is "one billion, two hundred twenty-one million, sixteen thousand, five hundred fifty-seven".