1666721004 has 48 divisors (see below), whose sum is σ = 4434540768. Its totient is φ = 482669568.

The previous prime is 1666720969. The next prime is 1666721047. The reversal of 1666721004 is 4001276661.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 311587 + ... + 316890.

It is an arithmetic number, because the mean of its divisors is an integer number (92386266).

Almost surely, 2^1666721004 is an apocalyptic number.

It is an amenable number.

1666721004 is an abundant number, since it is smaller than the sum of its proper divisors (2767819764).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1666721004 is a wasteful number, since it uses less digits than its factorization.

1666721004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 628514 (or 628512 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 1666721004 is about 40825.4945346655. The cubic root of 1666721004 is about 1185.6439861631.

Adding to 1666721004 its reverse (4001276661), we get a palindrome (5667997665).

The spelling of 1666721004 in words is "one billion, six hundred sixty-six million, seven hundred twenty-one thousand, four".