1257321665 has 8 divisors (see below), whose sum is σ = 1531305600. Its totient is φ = 990844272.

The previous prime is 1257321661. The next prime is 1257321671. The reversal of 1257321665 is 5661237521.

It is a happy number.

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 1257321665 - 2² = 1257321661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1257321661) 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, 1876265 + ... + 1876934.

It is an arithmetic number, because the mean of its divisors is an integer number (191413200).

Almost surely, 2^1257321665 is an apocalyptic number.

It is an amenable number.

1257321665 is a deficient number, since it is larger than the sum of its proper divisors (273983935).

1257321665 is an equidigital number, since it uses as much as digits as its factorization.

1257321665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3753271.

The product of its digits is 75600, while the sum is 38.

The square root of 1257321665 is about 35458.7318583166. The cubic root of 1257321665 is about 1079.3164584755.

The spelling of 1257321665 in words is "one billion, two hundred fifty-seven million, three hundred twenty-one thousand, six hundred sixty-five".