21349440 has 224 divisors, whose sum is σ = 86319360. Its totient is φ = 4866048.

The previous prime is 21349403. The next prime is 21349453. The reversal of 21349440 is 4494312.

21349440 is a `hidden beast` number, since 213 + 4 + 9 + 440 = 666.

It is a tau number, because it is divible by the number of its divisors (224).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 60304 + ... + 60656.

Almost surely, 2^21349440 is an apocalyptic number.

21349440 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 21349440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43159680).

21349440 is an abundant number, since it is smaller than the sum of its proper divisors (64969920).

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

21349440 is a wasteful number, since it uses less digits than its factorization.

21349440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386 (or 370 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 21349440 is about 4620.5454223500. The cubic root of 21349440 is about 277.4142905500.

The spelling of 21349440 in words is "twenty-one million, three hundred forty-nine thousand, four hundred forty".