21680420 has 24 divisors (see below), whose sum is σ = 45650304. Its totient is φ = 8649056.

The previous prime is 21680419. The next prime is 21680443. The reversal of 21680420 is 2408612.

It is a super-2 number, since 2×21680420² = 940081222752800, which contains 22 as substring.

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, 7637 + ... + 10083.

It is an arithmetic number, because the mean of its divisors is an integer number (1902096).

Almost surely, 2^21680420 is an apocalyptic number.

21680420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21680420 is an abundant number, since it is smaller than the sum of its proper divisors (23969884).

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

21680420 is a wasteful number, since it uses less digits than its factorization.

21680420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2899 (or 2897 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21680420 is about 4656.2237918726. The cubic root of 21680420 is about 278.8405284197.

The spelling of 21680420 in words is "twenty-one million, six hundred eighty thousand, four hundred twenty".