21507834420 has 120 divisors (see below), whose sum is σ = 67517337888. Its totient is φ = 5731473600.

The previous prime is 21507834419. The next prime is 21507834431. The reversal of 21507834420 is 2443870512.

It is a happy number.

21507834420 is a `hidden beast` number, since 2 + 150 + 7 + 83 + 4 + 420 = 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 39 ways as a sum of consecutive naturals, for example, 2930155 + ... + 2937485.

Almost surely, 2^21507834420 is an apocalyptic number.

21507834420 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 21507834420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33758668944).

21507834420 is an abundant number, since it is smaller than the sum of its proper divisors (46009503468).

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

21507834420 is a wasteful number, since it uses less digits than its factorization.

21507834420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9163 (or 9152 counting only the distinct ones).

The product of its (nonzero) digits is 53760, while the sum is 36.

The spelling of 21507834420 in words is "twenty-one billion, five hundred seven million, eight hundred thirty-four thousand, four hundred twenty".