21036440 has 32 divisors (see below), whose sum is σ = 47494080. Its totient is φ = 8385792.

The previous prime is 21036413. The next prime is 21036443. The reversal of 21036440 is 4463012.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21036443) 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, 13964 + ... + 15396.

It is an arithmetic number, because the mean of its divisors is an integer number (1484190).

Almost surely, 2^21036440 is an apocalyptic number.

21036440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21036440 is an abundant number, since it is smaller than the sum of its proper divisors (26457640).

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

21036440 is a wasteful number, since it uses less digits than its factorization.

21036440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1811 (or 1807 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21036440 is about 4586.5499016145. The cubic root of 21036440 is about 276.0519051018.

Adding to 21036440 its reverse (4463012), we get a palindrome (25499452).

The spelling of 21036440 in words is "twenty-one million, thirty-six thousand, four hundred forty".