21029865408 has 196 divisors, whose sum is σ = 62754787368. Its totient is φ = 6989068800.

The previous prime is 21029865401. The next prime is 21029865413. The reversal of 21029865408 is 80456892012.

21029865408 is a `hidden beast` number, since 2 + 1 + 0 + 29 + 86 + 540 + 8 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21029865401) 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 27 ways as a sum of consecutive naturals, for example, 29999458 + ... + 30000158.

Almost surely, 2^21029865408 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21029865408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31377393684).

21029865408 is an abundant number, since it is smaller than the sum of its proper divisors (41724921960).

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

21029865408 is an frugal number, since it uses more digits than its factorization.

21029865408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1374 (or 1349 counting only the distinct ones).

The product of its (nonzero) digits is 276480, while the sum is 45.

The spelling of 21029865408 in words is "twenty-one billion, twenty-nine million, eight hundred sixty-five thousand, four hundred eight".