21290720 has 48 divisors (see below), whose sum is σ = 54876528. Its totient is φ = 7741440.

The previous prime is 21290701. The next prime is 21290729. The reversal of 21290720 is 2709212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21290729) 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, 4289 + ... + 7808.

It is an arithmetic number, because the mean of its divisors is an integer number (1143261).

Almost surely, 2^21290720 is an apocalyptic number.

21290720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21290720 is an abundant number, since it is smaller than the sum of its proper divisors (33585808).

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

21290720 is a wasteful number, since it uses less digits than its factorization.

21290720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12123 (or 12115 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 21290720 is about 4614.1868189314. The cubic root of 21290720 is about 277.1597214280.

Adding to 21290720 its reverse (2709212), we get a palindrome (23999932).

The spelling of 21290720 in words is "twenty-one million, two hundred ninety thousand, seven hundred twenty".