21535420 has 12 divisors (see below), whose sum is σ = 45224424. Its totient is φ = 8614160.

The previous prime is 21535411. The next prime is 21535433. The reversal of 21535420 is 2453512.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21535391 and 21535400.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 538366 + ... + 538405.

It is an arithmetic number, because the mean of its divisors is an integer number (3768702).

Almost surely, 2^21535420 is an apocalyptic number.

21535420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21535420 is an abundant number, since it is smaller than the sum of its proper divisors (23689004).

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

21535420 is a wasteful number, since it uses less digits than its factorization.

21535420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1076780 (or 1076778 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21535420 is about 4640.6271127941. The cubic root of 21535420 is about 278.2175031277.

Adding to 21535420 its reverse (2453512), we get a palindrome (23988932).

The spelling of 21535420 in words is "twenty-one million, five hundred thirty-five thousand, four hundred twenty".