21982640 has 20 divisors (see below), whose sum is σ = 51109824. Its totient is φ = 8793024.

The previous prime is 21982637. The next prime is 21982643. The reversal of 21982640 is 4628912.

It is an interprime number because it is at equal distance from previous prime (21982637) and next prime (21982643).

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×21982640² = 966472922739200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21982597 and 21982606.

It is not an unprimeable number, because it can be changed into a prime (21982643) 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, 137312 + ... + 137471.

Almost surely, 2^21982640 is an apocalyptic number.

21982640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21982640 is an abundant number, since it is smaller than the sum of its proper divisors (29127184).

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

21982640 is a wasteful number, since it uses less digits than its factorization.

21982640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274796 (or 274790 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21982640 is about 4688.5648123920. The cubic root of 21982640 is about 280.1302115457.

It can be divided in two parts, 21982 and 640, that added together give a palindrome (22622).

The spelling of 21982640 in words is "twenty-one million, nine hundred eighty-two thousand, six hundred forty".