6557121720 has 224 divisors, whose sum is σ = 22333924800. Its totient is φ = 1731684096.

The previous prime is 6557121661. The next prime is 6557121733. The reversal of 6557121720 is 271217556.

6557121720 is a `hidden beast` number, since 65 + 571 + 2 + 1 + 7 + 20 = 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 polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 3177409 + ... + 3179471.

Almost surely, 2^6557121720 is an apocalyptic number.

6557121720 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 6557121720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (11166962400).

6557121720 is an abundant number, since it is smaller than the sum of its proper divisors (15776803080).

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

6557121720 is a wasteful number, since it uses less digits than its factorization.

6557121720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2201 (or 2182 counting only the distinct ones).

The product of its (nonzero) digits is 29400, while the sum is 36.

The square root of 6557121720 is about 80976.0564611540. The cubic root of 6557121720 is about 1871.7064998442.

The spelling of 6557121720 in words is "six billion, five hundred fifty-seven million, one hundred twenty-one thousand, seven hundred twenty".