21789860 has 24 divisors (see below), whose sum is σ = 46876536. Its totient is φ = 8503040.

The previous prime is 21789851. The next prime is 21789877. The reversal of 21789860 is 6898712.

It can be written as a sum of positive squares in 4 ways, for example, as 3625216 + 18164644 = 1904^2 + 4262^2 .

It is a Harshad number since it is a multiple of its sum of digits (41).

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, 12467 + ... + 14106.

It is an arithmetic number, because the mean of its divisors is an integer number (1953189).

Almost surely, 2^21789860 is an apocalyptic number.

21789860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21789860 is an abundant number, since it is smaller than the sum of its proper divisors (25086676).

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

21789860 is a wasteful number, since it uses less digits than its factorization.

21789860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26623 (or 26621 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21789860 is about 4667.9610109768. The cubic root of 21789860 is about 279.3089249955.

Adding to 21789860 its sum of digits (41), we get a triangular number (21789901 = T₆₆₀₁).

The spelling of 21789860 in words is "twenty-one million, seven hundred eighty-nine thousand, eight hundred sixty".