21172369920 has 320 divisors, whose sum is σ = 73395552384. Its totient is φ = 5175705600.

The previous prime is 21172369919. The next prime is 21172369927. The reversal of 21172369920 is 2996327112.

It is a tau number, because it is divible by the number of its divisors (320).

It is a super-3 number, since 3×21172369920³ (a number of 32 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21172369927) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 16273270 + ... + 16274570.

Almost surely, 2^21172369920 is an apocalyptic number.

21172369920 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 21172369920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36697776192).

21172369920 is an abundant number, since it is smaller than the sum of its proper divisors (52223182464).

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

21172369920 is a wasteful number, since it uses less digits than its factorization.

21172369920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1503 (or 1487 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 42.

The spelling of 21172369920 in words is "twenty-one billion, one hundred seventy-two million, three hundred sixty-nine thousand, nine hundred twenty".