1620621666 has 24 divisors (see below), whose sum is σ = 3512496000. Its totient is φ = 540030456.

The previous prime is 1620621649. The next prime is 1620621671. The reversal of 1620621666 is 6661260261.

It is a happy number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1620621666.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 49335 + ... + 75333.

It is an arithmetic number, because the mean of its divisors is an integer number (146354000).

Almost surely, 2^1620621666 is an apocalyptic number.

1620621666 is an abundant number, since it is smaller than the sum of its proper divisors (1891874334).

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

1620621666 is a wasteful number, since it uses less digits than its factorization.

1620621666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29470 (or 29467 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 1620621666 is about 40256.9455622257. The cubic root of 1620621666 is about 1174.6105040088.

It can be divided in two parts, 1620 and 621666, that added together give a triangular number (623286 = T₁₁₁₆).

The spelling of 1620621666 in words is "one billion, six hundred twenty million, six hundred twenty-one thousand, six hundred sixty-six".