21481840 has 40 divisors (see below), whose sum is σ = 50184288. Its totient is φ = 8551680.

The previous prime is 21481807. The next prime is 21481847. The reversal of 21481840 is 4818412.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×21481840² = 922938899571200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21481799 and 21481808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481847) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20530 + ... + 21550.

Almost surely, 2^21481840 is an apocalyptic number.

21481840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21481840 is an abundant number, since it is smaller than the sum of its proper divisors (28702448).

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

21481840 is a wasteful number, since it uses less digits than its factorization.

21481840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1297 (or 1291 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 28.

The square root of 21481840 is about 4634.8505909037. The cubic root of 21481840 is about 277.9865769963.

The spelling of 21481840 in words is "twenty-one million, four hundred eighty-one thousand, eight hundred forty".