1666821398 has 32 divisors (see below), whose sum is σ = 2887073280. Its totient is φ = 713772000.

The previous prime is 1666821383. The next prime is 1666821407. The reversal of 1666821398 is 8931286661.

It is a congruent number.

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, 64643 + ... + 86673.

It is an arithmetic number, because the mean of its divisors is an integer number (90221040).

Almost surely, 2^1666821398 is an apocalyptic number.

1666821398 is a deficient number, since it is larger than the sum of its proper divisors (1220251882).

1666821398 is a wasteful number, since it uses less digits than its factorization.

1666821398 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22244.

The product of its digits is 746496, while the sum is 50.

The square root of 1666821398 is about 40826.7240664739. The cubic root of 1666821398 is about 1185.6677912175.

The spelling of 1666821398 in words is "one billion, six hundred sixty-six million, eight hundred twenty-one thousand, three hundred ninety-eight".