21151240 has 64 divisors (see below), whose sum is σ = 52954560. Its totient is φ = 7537920.

The previous prime is 21151219. The next prime is 21151241. The reversal of 21151240 is 4215112.

It is not an unprimeable number, because it can be changed into a prime (21151241) 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, 22867 + ... + 23773.

It is an arithmetic number, because the mean of its divisors is an integer number (827415).

Almost surely, 2^21151240 is an apocalyptic number.

21151240 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 21151240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26477280).

21151240 is an abundant number, since it is smaller than the sum of its proper divisors (31803320).

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

21151240 is a wasteful number, since it uses less digits than its factorization.

21151240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 982 (or 978 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21151240 is about 4599.0477275193. The cubic root of 21151240 is about 276.5531509602.

Adding to 21151240 its reverse (4215112), we get a palindrome (25366352).

The spelling of 21151240 in words is "twenty-one million, one hundred fifty-one thousand, two hundred forty".