21511420 has 48 divisors (see below), whose sum is σ = 54351360. Its totient is φ = 6986304.

The previous prime is 21511403. The next prime is 21511423. The reversal of 21511420 is 2411512.

It is a junction number, because it is equal to n+sod(n) for n = 21511394 and 21511403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21511423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1384 + ... + 6703.

It is an arithmetic number, because the mean of its divisors is an integer number (1132320).

Almost surely, 2^21511420 is an apocalyptic number.

21511420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21511420 is an abundant number, since it is smaller than the sum of its proper divisors (32839940).

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

21511420 is a wasteful number, since it uses less digits than its factorization.

21511420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8122 (or 8120 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21511420 is about 4638.0405345361. The cubic root of 21511420 is about 278.1141121858.

Adding to 21511420 its reverse (2411512), we get a palindrome (23922932).

The spelling of 21511420 in words is "twenty-one million, five hundred eleven thousand, four hundred twenty".