21908780 has 12 divisors (see below), whose sum is σ = 46008480. Its totient is φ = 8763504.

The previous prime is 21908771. The next prime is 21908791. The reversal of 21908780 is 8780912.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21908780.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 547700 + ... + 547739.

It is an arithmetic number, because the mean of its divisors is an integer number (3834040).

Almost surely, 2^21908780 is an apocalyptic number.

21908780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21908780 is an abundant number, since it is smaller than the sum of its proper divisors (24099700).

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

21908780 is a wasteful number, since it uses less digits than its factorization.

21908780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1095448 (or 1095446 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 21908780 is about 4680.6815743009. The cubic root of 21908780 is about 279.8161207674.

The spelling of 21908780 in words is "twenty-one million, nine hundred eight thousand, seven hundred eighty".