21559988 has 6 divisors (see below), whose sum is σ = 37729986. Its totient is φ = 10779992.

The previous prime is 21559949. The next prime is 21559991. The reversal of 21559988 is 88995512.

It can be written as a sum of positive squares in only one way, i.e., 21270544 + 289444 = 4612^2 + 538^2 .

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 as a sum of consecutive naturals, namely, 2694995 + ... + 2695002.

It is an arithmetic number, because the mean of its divisors is an integer number (6288331).

Almost surely, 2^21559988 is an apocalyptic number.

It is an amenable number.

21559988 is a deficient number, since it is larger than the sum of its proper divisors (16169998).

21559988 is a wasteful number, since it uses less digits than its factorization.

21559988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5390001 (or 5389999 counting only the distinct ones).

The product of its digits is 259200, while the sum is 47.

The square root of 21559988 is about 4643.2734143059. The cubic root of 21559988 is about 278.3232614552.

The spelling of 21559988 in words is "twenty-one million, five hundred fifty-nine thousand, nine hundred eighty-eight".