21671440 has 40 divisors (see below), whose sum is σ = 57585600. Its totient is φ = 7430016.

The previous prime is 21671431. The next prime is 21671471. The reversal of 21671440 is 4417612.

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

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, 18790 + ... + 19909.

It is an arithmetic number, because the mean of its divisors is an integer number (1439640).

Almost surely, 2^21671440 is an apocalyptic number.

21671440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21671440 is an abundant number, since it is smaller than the sum of its proper divisors (35914160).

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

21671440 is a wasteful number, since it uses less digits than its factorization.

21671440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38719 (or 38713 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21671440 is about 4655.2593912692. The cubic root of 21671440 is about 278.8020246493.

The spelling of 21671440 in words is "twenty-one million, six hundred seventy-one thousand, four hundred forty".