21791440 has 40 divisors (see below), whose sum is σ = 55273248. Its totient is φ = 7923840.

The previous prime is 21791353. The next prime is 21791477. The reversal of 21791440 is 4419712.

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

It is a junction number, because it is equal to n+sod(n) for n = 21791399 and 21791408.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11502 + ... + 13261.

Almost surely, 2^21791440 is an apocalyptic number.

21791440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21791440 is an abundant number, since it is smaller than the sum of its proper divisors (33481808).

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

21791440 is a wasteful number, since it uses less digits than its factorization.

21791440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24787 (or 24781 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21791440 is about 4668.1302466834. The cubic root of 21791440 is about 279.3156758027.

The spelling of 21791440 in words is "twenty-one million, seven hundred ninety-one thousand, four hundred forty".