21729708 has 240 divisors, whose sum is σ = 77409024. Its totient is φ = 5132160.

The previous prime is 21729683. The next prime is 21729709. The reversal of 21729708 is 80792712.

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

It is not an unprimeable number, because it can be changed into a prime (21729709) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 324291 + ... + 324357.

Almost surely, 2^21729708 is an apocalyptic number.

21729708 is a gapful number since it is divisible by the number (28) 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 21729708, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38704512).

21729708 is an abundant number, since it is smaller than the sum of its proper divisors (55679316).

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

21729708 is a wasteful number, since it uses less digits than its factorization.

21729708 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114 (or 103 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 21729708 is about 4661.5134881281. The cubic root of 21729708 is about 279.0516727047.

The spelling of 21729708 in words is "twenty-one million, seven hundred twenty-nine thousand, seven hundred eight".