21049840 has 40 divisors (see below), whose sum is σ = 55933920. Its totient is φ = 7216896.

The previous prime is 21049817. The next prime is 21049841. The reversal of 21049840 is 4894012.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 21049799 and 21049808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21049841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18235 + ... + 19354.

It is an arithmetic number, because the mean of its divisors is an integer number (1398348).

Almost surely, 2^21049840 is an apocalyptic number.

21049840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21049840 is an abundant number, since it is smaller than the sum of its proper divisors (34884080).

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

21049840 is a wasteful number, since it uses less digits than its factorization.

21049840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37609 (or 37603 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 21049840 is about 4588.0104620630. The cubic root of 21049840 is about 276.1105067533.

The spelling of 21049840 in words is "twenty-one million, forty-nine thousand, eight hundred forty".