21439780 has 24 divisors (see below), whose sum is σ = 45150840. Its totient is φ = 8551680.

The previous prime is 21439753. The next prime is 21439783. The reversal of 21439780 is 8793412.

It can be written as a sum of positive squares in 4 ways, for example, as 9784384 + 11655396 = 3128^2 + 3414^2 .

It is not an unprimeable number, because it can be changed into a prime (21439783) 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, 6870 + ... + 9490.

It is an arithmetic number, because the mean of its divisors is an integer number (1881285).

Almost surely, 2^21439780 is an apocalyptic number.

21439780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21439780 is an abundant number, since it is smaller than the sum of its proper divisors (23711060).

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

21439780 is a wasteful number, since it uses less digits than its factorization.

21439780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3039 (or 3037 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21439780 is about 4630.3110046734. The cubic root of 21439780 is about 277.8050321110.

The spelling of 21439780 in words is "twenty-one million, four hundred thirty-nine thousand, seven hundred eighty".