21431040 has 72 divisors (see below), whose sum is σ = 68457648. Its totient is φ = 5713920.

The previous prime is 21431023. The next prime is 21431057. The reversal of 21431040 is 4013412.

It is an interprime number because it is at equal distance from previous prime (21431023) and next prime (21431057).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1050 + ... + 6630.

Almost surely, 2^21431040 is an apocalyptic number.

21431040 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 21431040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34228824).

21431040 is an abundant number, since it is smaller than the sum of its proper divisors (47026608).

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

21431040 is an equidigital number, since it uses as much as digits as its factorization.

21431040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5605 (or 5591 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21431040 is about 4629.3671273728. The cubic root of 21431040 is about 277.7672775883.

Adding to 21431040 its reverse (4013412), we get a palindrome (25444452).

The spelling of 21431040 in words is "twenty-one million, four hundred thirty-one thousand, forty".