21709798 has 16 divisors (see below), whose sum is σ = 35716176. Its totient is φ = 9815040.

The previous prime is 21709781. The next prime is 21709813. The reversal of 21709798 is 89790712.

It is a happy number.

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 7 ways as a sum of consecutive naturals, for example, 1690 + ... + 6802.

It is an arithmetic number, because the mean of its divisors is an integer number (2232261).

Almost surely, 2^21709798 is an apocalyptic number.

21709798 is a deficient number, since it is larger than the sum of its proper divisors (14006378).

21709798 is a wasteful number, since it uses less digits than its factorization.

21709798 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5319.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 21709798 is about 4659.3774262234. The cubic root of 21709798 is about 278.9664189659.

The spelling of 21709798 in words is "twenty-one million, seven hundred nine thousand, seven hundred ninety-eight".