21731420 has 24 divisors (see below), whose sum is σ = 45771264. Its totient is φ = 8666816.

The previous prime is 21731419. The next prime is 21731441. The reversal of 21731420 is 2413712.

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

It is a junction number, because it is equal to n+sod(n) for n = 21731392 and 21731401.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6242 + ... + 9078.

It is an arithmetic number, because the mean of its divisors is an integer number (1907136).

Almost surely, 2^21731420 is an apocalyptic number.

21731420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21731420 is an abundant number, since it is smaller than the sum of its proper divisors (24039844).

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

21731420 is a wasteful number, since it uses less digits than its factorization.

21731420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3229 (or 3227 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 21731420 is about 4661.6971158581. The cubic root of 21731420 is about 279.0590009811.

The spelling of 21731420 in words is "twenty-one million, seven hundred thirty-one thousand, four hundred twenty".