21272240 has 80 divisors (see below), whose sum is σ = 56353536. Its totient is φ = 7392000.

The previous prime is 21272213. The next prime is 21272269. The reversal of 21272240 is 4227212.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19715 + ... + 20765.

Almost surely, 2^21272240 is an apocalyptic number.

21272240 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 21272240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28176768).

21272240 is an abundant number, since it is smaller than the sum of its proper divisors (35081296).

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

21272240 is a wasteful number, since it uses less digits than its factorization.

21272240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1098 (or 1092 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 21272240 is about 4612.1838645050. The cubic root of 21272240 is about 277.0795081664.

Adding to 21272240 its reverse (4227212), we get a palindrome (25499452).

It can be divided in two parts, 21272 and 240, that added together give a palindrome (21512).

The spelling of 21272240 in words is "twenty-one million, two hundred seventy-two thousand, two hundred forty".