1212123561 has 16 divisors (see below), whose sum is σ = 1800603648. Its totient is φ = 718989200.

The previous prime is 1212123503. The next prime is 1212123581. The reversal of 1212123561 is 1653212121.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1212123561 - 2¹⁹ = 1211599273 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1212123581) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 389205 + ... + 392306.

It is an arithmetic number, because the mean of its divisors is an integer number (112537728).

Almost surely, 2^1212123561 is an apocalyptic number.

1212123561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1212123561 is a deficient number, since it is larger than the sum of its proper divisors (588480087).

1212123561 is a wasteful number, since it uses less digits than its factorization.

1212123561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 781572.

The product of its digits is 720, while the sum is 24.

The square root of 1212123561 is about 34815.5649243266. The cubic root of 1212123561 is about 1066.2252529799.

Adding to 1212123561 its reverse (1653212121), we get a palindrome (2865335682).

The spelling of 1212123561 in words is "one billion, two hundred twelve million, one hundred twenty-three thousand, five hundred sixty-one".