21001551320 has 64 divisors (see below), whose sum is σ = 47471961600. Its totient is φ = 8361884160.

The previous prime is 21001551289. The next prime is 21001551419. The reversal of 21001551320 is 2315510012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21001551292 and 21001551301.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9378761 + ... + 9380999.

It is an arithmetic number, because the mean of its divisors is an integer number (741749400).

Almost surely, 2^21001551320 is an apocalyptic number.

21001551320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001551320 is an abundant number, since it is smaller than the sum of its proper divisors (26470410280).

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

21001551320 is a wasteful number, since it uses less digits than its factorization.

21001551320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3228 (or 3224 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 20.

The spelling of 21001551320 in words is "twenty-one billion, one million, five hundred fifty-one thousand, three hundred twenty".