21247680 has 56 divisors (see below), whose sum is σ = 67464432. Its totient is φ = 5665792.

The previous prime is 21247669. The next prime is 21247693. The reversal of 21247680 is 8674212.

It is a Harshad number since it is a multiple of its sum of digits (30).

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, 10107 + ... + 12026.

It is an arithmetic number, because the mean of its divisors is an integer number (1204722).

Almost surely, 2^21247680 is an apocalyptic number.

21247680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21247680 is an abundant number, since it is smaller than the sum of its proper divisors (46216752).

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

21247680 is a wasteful number, since it uses less digits than its factorization.

21247680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22153 (or 22143 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21247680 is about 4609.5205824467. The cubic root of 21247680 is about 276.9728324653.

The spelling of 21247680 in words is "twenty-one million, two hundred forty-seven thousand, six hundred eighty".