21573396 has 72 divisors (see below), whose sum is σ = 60662784. Its totient is φ = 6419520.

The previous prime is 21573371. The next prime is 21573407. The reversal of 21573396 is 69337512.

It is a super-2 number, since 2×21573396² = 930822829945632, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21573396.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13765 + ... + 15251.

Almost surely, 2^21573396 is an apocalyptic number.

21573396 is a gapful number since it is divisible by the number (26) 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 21573396, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30331392).

21573396 is an abundant number, since it is smaller than the sum of its proper divisors (39089388).

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

21573396 is a wasteful number, since it uses less digits than its factorization.

21573396 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1541 (or 1536 counting only the distinct ones).

The product of its digits is 34020, while the sum is 36.

The square root of 21573396 is about 4644.7169989139. The cubic root of 21573396 is about 278.3809452377.

The spelling of 21573396 in words is "twenty-one million, five hundred seventy-three thousand, three hundred ninety-six".