21072040 has 64 divisors (see below), whose sum is σ = 52436160. Its totient is φ = 7557120.

The previous prime is 21072031. The next prime is 21072041. The reversal of 21072040 is 4027012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072041) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36232 + ... + 36808.

It is an arithmetic number, because the mean of its divisors is an integer number (819315).

Almost surely, 2^21072040 is an apocalyptic number.

21072040 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 21072040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26218080).

21072040 is an abundant number, since it is smaller than the sum of its proper divisors (31364120).

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

21072040 is a wasteful number, since it uses less digits than its factorization.

21072040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 682 (or 678 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 16.

The square root of 21072040 is about 4590.4291738355. The cubic root of 21072040 is about 276.2075383642.

Adding to 21072040 its reverse (4027012), we get a palindrome (25099052).

The spelling of 21072040 in words is "twenty-one million, seventy-two thousand, forty".