21431020 has 48 divisors (see below), whose sum is σ = 48898080. Its totient is φ = 7842816.

The previous prime is 21431017. The next prime is 21431023. The reversal of 21431020 is 2013412.

It is an interprime number because it is at equal distance from previous prime (21431017) and next prime (21431023).

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21431023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35844 + ... + 36436.

It is an arithmetic number, because the mean of its divisors is an integer number (1018710).

Almost surely, 2^21431020 is an apocalyptic number.

21431020 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 21431020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24449040).

21431020 is an abundant number, since it is smaller than the sum of its proper divisors (27467060).

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

21431020 is a wasteful number, since it uses less digits than its factorization.

21431020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 754 (or 752 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21431020 is about 4629.3649672498. The cubic root of 21431020 is about 277.7671911817.

Adding to 21431020 its reverse (2013412), we get a palindrome (23444432).

The spelling of 21431020 in words is "twenty-one million, four hundred thirty-one thousand, twenty".