21019988 has 12 divisors (see below), whose sum is σ = 40129152. Its totient is φ = 9554520.

The previous prime is 21019987. The next prime is 21019993. The reversal of 21019988 is 88991012.

It is a hoax number, since the sum of its digits (38) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 238820 + ... + 238907.

It is an arithmetic number, because the mean of its divisors is an integer number (3344096).

Almost surely, 2^21019988 is an apocalyptic number.

It is an amenable number.

21019988 is a deficient number, since it is larger than the sum of its proper divisors (19109164).

21019988 is a wasteful number, since it uses less digits than its factorization.

21019988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 477742 (or 477740 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 21019988 is about 4584.7560458546. The cubic root of 21019988 is about 275.9799222250.

The spelling of 21019988 in words is "twenty-one million, nineteen thousand, nine hundred eighty-eight".