21430720 has 56 divisors (see below), whose sum is σ = 51444144. Its totient is φ = 8503296.

The previous prime is 21430697. The next prime is 21430723. The reversal of 21430720 is 2703412.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21430723) 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, 61587 + ... + 61933.

Almost surely, 2^21430720 is an apocalyptic number.

21430720 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 21430720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25722072).

21430720 is an abundant number, since it is smaller than the sum of its proper divisors (30013424).

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

21430720 is a wasteful number, since it uses less digits than its factorization.

21430720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 557 (or 547 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21430720 is about 4629.3325652841. The cubic root of 21430720 is about 277.7658950769.

The spelling of 21430720 in words is "twenty-one million, four hundred thirty thousand, seven hundred twenty".