1257120561 has 4 divisors (see below), whose sum is σ = 1676160752. Its totient is φ = 838080372.

The previous prime is 1257120559. The next prime is 1257120577. The reversal of 1257120561 is 1650217521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1650217521 = 3 ⋅550072507.

It is not a de Polignac number, because 1257120561 - 2¹ = 1257120559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1257120581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 209520091 + ... + 209520096.

It is an arithmetic number, because the mean of its divisors is an integer number (419040188).

Almost surely, 2^1257120561 is an apocalyptic number.

It is an amenable number.

1257120561 is a deficient number, since it is larger than the sum of its proper divisors (419040191).

1257120561 is an equidigital number, since it uses as much as digits as its factorization.

1257120561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419040190.

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

The square root of 1257120561 is about 35455.8959977040. The cubic root of 1257120561 is about 1079.2589111677.

The spelling of 1257120561 in words is "one billion, two hundred fifty-seven million, one hundred twenty thousand, five hundred sixty-one".