21768940 has 12 divisors (see below), whose sum is σ = 45714816. Its totient is φ = 8707568.

The previous prime is 21768931. The next prime is 21768941. The reversal of 21768940 is 4986712.

It is a self number, because there is not a number n which added to its sum of digits gives 21768940.

It is not an unprimeable number, because it can be changed into a prime (21768941) 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, 544204 + ... + 544243.

It is an arithmetic number, because the mean of its divisors is an integer number (3809568).

Almost surely, 2^21768940 is an apocalyptic number.

21768940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21768940 is an abundant number, since it is smaller than the sum of its proper divisors (23945876).

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

21768940 is a wasteful number, since it uses less digits than its factorization.

21768940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1088456 (or 1088454 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21768940 is about 4665.7196658179. The cubic root of 21768940 is about 279.2195101075.

The spelling of 21768940 in words is "twenty-one million, seven hundred sixty-eight thousand, nine hundred forty".