21305790 has 48 divisors (see below), whose sum is σ = 60433776. Its totient is φ = 5164800.

The previous prime is 21305789. The next prime is 21305839. The reversal of 21305790 is 9750312.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9771 + ... + 11750.

It is an arithmetic number, because the mean of its divisors is an integer number (1259037).

Almost surely, 2^21305790 is an apocalyptic number.

21305790 is an abundant number, since it is smaller than the sum of its proper divisors (39127986).

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

21305790 is a wasteful number, since it uses less digits than its factorization.

21305790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21545 (or 21542 counting only the distinct ones).

The product of its (nonzero) digits is 1890, while the sum is 27.

The square root of 21305790 is about 4615.8195372003. The cubic root of 21305790 is about 277.2250990810.

The spelling of 21305790 in words is "twenty-one million, three hundred five thousand, seven hundred ninety".