1221015557 has 2 divisors, whose sum is σ = 1221015558. Its totient is φ = 1221015556.

The previous prime is 1221015541. The next prime is 1221015581. The reversal of 1221015557 is 7555101221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 751253281 + 469762276 = 27409^2 + 21674^2 .

It is an emirp because it is prime and its reverse (7555101221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221015557 - 2⁴ = 1221015541 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221015517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610507778 + 610507779.

It is an arithmetic number, because the mean of its divisors is an integer number (610507779).

Almost surely, 2^1221015557 is an apocalyptic number.

It is an amenable number.

1221015557 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221015557 is an equidigital number, since it uses as much as digits as its factorization.

1221015557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3500, while the sum is 29.

The square root of 1221015557 is about 34943.0330251969. The cubic root of 1221015557 is about 1068.8261377675.

Adding to 1221015557 its reverse (7555101221), we get a palindrome (8776116778).

The spelling of 1221015557 in words is "one billion, two hundred twenty-one million, fifteen thousand, five hundred fifty-seven".