21275757720 has 384 divisors, whose sum is σ = 85720602240. Its totient is φ = 4464967680.

The previous prime is 21275757719. The next prime is 21275757733. The reversal of 21275757720 is 2775757212.

21275757720 is a `hidden beast` number, since 2 + 1 + 2 + 7 + 57 + 577 + 20 = 666.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1750384 + ... + 1762496.

It is an arithmetic number, because the mean of its divisors is an integer number (223230735).

Almost surely, 2^21275757720 is an apocalyptic number.

21275757720 is a gapful number since it is divisible by the number (20) 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 21275757720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42860301120).

21275757720 is an abundant number, since it is smaller than the sum of its proper divisors (64444844520).

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

21275757720 is a wasteful number, since it uses less digits than its factorization.

21275757720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12195 (or 12188 counting only the distinct ones).

The product of its (nonzero) digits is 480200, while the sum is 45.

The spelling of 21275757720 in words is "twenty-one billion, two hundred seventy-five million, seven hundred fifty-seven thousand, seven hundred twenty".