1666420521 has 8 divisors (see below), whose sum is σ = 2244800544. Its totient is φ = 1099493760.

The previous prime is 1666420507. The next prime is 1666420573. The reversal of 1666420521 is 1250246661.

1666420521 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1666420521 - 2²⁶ = 1599311657 is a prime.

It is a super-2 number, since 2×1666420521² = 5553914705619822882, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1666420621) 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, 2862975 + ... + 2863556.

It is an arithmetic number, because the mean of its divisors is an integer number (280600068).

Almost surely, 2^1666420521 is an apocalyptic number.

It is an amenable number.

1666420521 is a deficient number, since it is larger than the sum of its proper divisors (578380023).

1666420521 is an equidigital number, since it uses as much as digits as its factorization.

1666420521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5726631.

The product of its (nonzero) digits is 17280, while the sum is 33.

The square root of 1666420521 is about 40821.8142786427. The cubic root of 1666420521 is about 1185.5727310315.

The spelling of 1666420521 in words is "one billion, six hundred sixty-six million, four hundred twenty thousand, five hundred twenty-one".