21613020 has 144 divisors (see below), whose sum is σ = 71947680. Its totient is φ = 4815360.

The previous prime is 21613019. The next prime is 21613043. The reversal of 21613020 is 2031612.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a zygodrome in base 11.

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 94266 + ... + 94494.

Almost surely, 2^21613020 is an apocalyptic number.

21613020 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 21613020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35973840).

21613020 is an abundant number, since it is smaller than the sum of its proper divisors (50334660).

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

21613020 is a wasteful number, since it uses less digits than its factorization.

21613020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276 (or 263 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21613020 is about 4648.9805334073. The cubic root of 21613020 is about 278.5512757094.

Adding to 21613020 its reverse (2031612), we get a palindrome (23644632).

The spelling of 21613020 in words is "twenty-one million, six hundred thirteen thousand, twenty".