21720468 has 72 divisors (see below), whose sum is σ = 63695296. Its totient is φ = 5639040.

The previous prime is 21720467. The next prime is 21720469. The reversal of 21720468 is 86402712.

It is an interprime number because it is at equal distance from previous prime (21720467) and next prime (21720469).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720463) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9096 + ... + 11232.

Almost surely, 2^21720468 is an apocalyptic number.

21720468 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21720468, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31847648).

21720468 is an abundant number, since it is smaller than the sum of its proper divisors (41974828).

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

21720468 is a wasteful number, since it uses less digits than its factorization.

21720468 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2173 (or 2160 counting only the distinct ones).

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

The square root of 21720468 is about 4660.5222883278. The cubic root of 21720468 is about 279.0121139124.

The spelling of 21720468 in words is "twenty-one million, seven hundred twenty thousand, four hundred sixty-eight".