21381400 has 24 divisors (see below), whose sum is σ = 49712220. Its totient is φ = 8552480.

The previous prime is 21381389. The next prime is 21381407. The reversal of 21381400 is 418312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381407) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 53254 + ... + 53653.

Almost surely, 2^21381400 is an apocalyptic number.

21381400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21381400 is an abundant number, since it is smaller than the sum of its proper divisors (28330820).

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

21381400 is a wasteful number, since it uses less digits than its factorization.

21381400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106923 (or 106914 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21381400 is about 4624.0025951550. The cubic root of 21381400 is about 277.5526507787.

Adding to 21381400 its reverse (418312), we get a palindrome (21799712).

The spelling of 21381400 in words is "twenty-one million, three hundred eighty-one thousand, four hundred".