21029742720 has 512 divisors, whose sum is σ = 88833024000. Its totient is φ = 4597198848.

The previous prime is 21029742683. The next prime is 21029742779. The reversal of 21029742720 is 2724792012.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2778301 + ... + 2785859.

It is an arithmetic number, because the mean of its divisors is an integer number (173502000).

Almost surely, 2^21029742720 is an apocalyptic number.

21029742720 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 21029742720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44416512000).

21029742720 is an abundant number, since it is smaller than the sum of its proper divisors (67803281280).

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

21029742720 is a wasteful number, since it uses less digits than its factorization.

21029742720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7617 (or 7599 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 36.

The spelling of 21029742720 in words is "twenty-one billion, twenty-nine million, seven hundred forty-two thousand, seven hundred twenty".