21447640 has 16 divisors (see below), whose sum is σ = 48257280. Its totient is φ = 8579040.

The previous prime is 21447611. The next prime is 21447683. The reversal of 21447640 is 4674412.

It is a junction number, because it is equal to n+sod(n) for n = 21447599 and 21447608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 268056 + ... + 268135.

It is an arithmetic number, because the mean of its divisors is an integer number (3016080).

Almost surely, 2^21447640 is an apocalyptic number.

21447640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21447640 is an abundant number, since it is smaller than the sum of its proper divisors (26809640).

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

21447640 is a wasteful number, since it uses less digits than its factorization.

21447640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 536202 (or 536198 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 28.

The square root of 21447640 is about 4631.1596819803. The cubic root of 21447640 is about 277.8389765012.

The spelling of 21447640 in words is "twenty-one million, four hundred forty-seven thousand, six hundred forty".