21235620 has 144 divisors (see below), whose sum is σ = 71705088. Its totient is φ = 4677120.

The previous prime is 21235609. The next prime is 21235631. The reversal of 21235620 is 2653212.

It is an interprime number because it is at equal distance from previous prime (21235609) and next prime (21235631).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 91024 + ... + 91256.

It is an arithmetic number, because the mean of its divisors is an integer number (497952).

Almost surely, 2^21235620 is an apocalyptic number.

21235620 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 21235620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35852544).

21235620 is an abundant number, since it is smaller than the sum of its proper divisors (50469468).

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

21235620 is a wasteful number, since it uses less digits than its factorization.

21235620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290 (or 281 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21235620 is about 4608.2122346958. The cubic root of 21235620 is about 276.9204200837.

Adding to 21235620 its reverse (2653212), we get a palindrome (23888832).

It can be divided in two parts, 21 and 235620, that added together give a triangular number (235641 = T₆₈₆).

The spelling of 21235620 in words is "twenty-one million, two hundred thirty-five thousand, six hundred twenty".