21545400 has 96 divisors (see below), whose sum is σ = 67518000. Its totient is φ = 5683200.

The previous prime is 21545393. The next prime is 21545429. The reversal of 21545400 is 454512.

It is a super-2 number, since 2×21545400² = 928408522320000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 89280 + ... + 89520.

Almost surely, 2^21545400 is an apocalyptic number.

21545400 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 21545400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33759000).

21545400 is an abundant number, since it is smaller than the sum of its proper divisors (45972600).

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

21545400 is a wasteful number, since it uses less digits than its factorization.

21545400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 409 (or 400 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21545400 is about 4641.7022739508. The cubic root of 21545400 is about 278.2604739153.

Adding to 21545400 its reverse (454512), we get a palindrome (21999912).

It can be divided in two parts, 21545 and 400, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21545400 in words is "twenty-one million, five hundred forty-five thousand, four hundred".