21415440 has 40 divisors (see below), whose sum is σ = 66388608. Its totient is φ = 5710720.

The previous prime is 21415439. The next prime is 21415441. The reversal of 21415440 is 4451412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21415439) and next prime (21415441).

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (21415441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44376 + ... + 44855.

Almost surely, 2^21415440 is an apocalyptic number.

21415440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21415440 is an abundant number, since it is smaller than the sum of its proper divisors (44973168).

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

21415440 is a wasteful number, since it uses less digits than its factorization.

21415440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89247 (or 89241 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 21.

The square root of 21415440 is about 4627.6819251111. The cubic root of 21415440 is about 277.6998641333.

Adding to 21415440 its reverse (4451412), we get a palindrome (25866852).

The spelling of 21415440 in words is "twenty-one million, four hundred fifteen thousand, four hundred forty".