661993020 has 192 divisors, whose sum is σ = 2234494080. Its totient is φ = 161740800.

The previous prime is 661993009. The next prime is 661993081. The reversal of 661993020 is 20399166.

661993020 is a `hidden beast` number, since 6 + 619 + 9 + 30 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1270360 + ... + 1270880.

It is an arithmetic number, because the mean of its divisors is an integer number (11637990).

Almost surely, 2^661993020 is an apocalyptic number.

661993020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661993020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1117247040).

661993020 is an abundant number, since it is smaller than the sum of its proper divisors (1572501060).

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

661993020 is a wasteful number, since it uses less digits than its factorization.

661993020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 733 (or 725 counting only the distinct ones).

The product of its (nonzero) digits is 17496, while the sum is 36.

The square root of 661993020 is about 25729.2250174777. The cubic root of 661993020 is about 871.5342724575.

The spelling of 661993020 in words is "six hundred sixty-one million, nine hundred ninety-three thousand, twenty".