21147640 has 16 divisors (see below), whose sum is σ = 47582280. Its totient is φ = 8459040.

The previous prime is 21147617. The next prime is 21147647. The reversal of 21147640 is 4674112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147647) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264306 + ... + 264385.

Almost surely, 2^21147640 is an apocalyptic number.

21147640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21147640 is an abundant number, since it is smaller than the sum of its proper divisors (26434640).

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

21147640 is a wasteful number, since it uses less digits than its factorization.

21147640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 528702 (or 528698 counting only the distinct ones).

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

The square root of 21147640 is about 4598.6563254934. The cubic root of 21147640 is about 276.5374600309.

The spelling of 21147640 in words is "twenty-one million, one hundred forty-seven thousand, six hundred forty".