1665221251 has 8 divisors (see below), whose sum is σ = 1705636800. Its totient is φ = 1625212200.

The previous prime is 1665221227. The next prime is 1665221293. The reversal of 1665221251 is 1521225661.

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 1665221251 - 2¹¹ = 1665219203 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1665221221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 93325 + ... + 109726.

It is an arithmetic number, because the mean of its divisors is an integer number (213204600).

Almost surely, 2^1665221251 is an apocalyptic number.

1665221251 is the 18250-th centered decagonal number.

1665221251 is a deficient number, since it is larger than the sum of its proper divisors (40415549).

1665221251 is a wasteful number, since it uses less digits than its factorization.

1665221251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203249.

The product of its digits is 7200, while the sum is 31.

The square root of 1665221251 is about 40807.1225523192. The cubic root of 1665221251 is about 1185.2882564130.

The spelling of 1665221251 in words is "one billion, six hundred sixty-five million, two hundred twenty-one thousand, two hundred fifty-one".