21152440 has 16 divisors (see below), whose sum is σ = 47593080. Its totient is φ = 8460960.

The previous prime is 21152423. The next prime is 21152441. The reversal of 21152440 is 4425112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21152441) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264366 + ... + 264445.

Almost surely, 2^21152440 is an apocalyptic number.

21152440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21152440 is an abundant number, since it is smaller than the sum of its proper divisors (26440640).

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

21152440 is a wasteful number, since it uses less digits than its factorization.

21152440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 528822 (or 528818 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 21152440 is about 4599.1781874591. The cubic root of 21152440 is about 276.5583808743.

Adding to 21152440 its reverse (4425112), we get a palindrome (25577552).

The spelling of 21152440 in words is "twenty-one million, one hundred fifty-two thousand, four hundred forty".