21408972 has 96 divisors (see below), whose sum is σ = 58705920. Its totient is φ = 6013440.

The previous prime is 21408971. The next prime is 21408973. The reversal of 21408972 is 27980412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21408971) and next prime (21408973).

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21408971) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 91768 + ... + 92000.

It is an arithmetic number, because the mean of its divisors is an integer number (611520).

Almost surely, 2^21408972 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 21408972, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29352960).

21408972 is an abundant number, since it is smaller than the sum of its proper divisors (37296948).

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

21408972 is a wasteful number, since it uses less digits than its factorization.

21408972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 303 (or 301 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21408972 is about 4626.9830343324. The cubic root of 21408972 is about 277.6719038769.

The spelling of 21408972 in words is "twenty-one million, four hundred eight thousand, nine hundred seventy-two".