21019999 has 48 divisors (see below), whose sum is σ = 30030336. Its totient is φ = 14287680.

The previous prime is 21019993. The next prime is 21020011. The reversal of 21019999 is 99991012.

It is not a de Polignac number, because 21019999 - 2⁵ = 21019967 is a prime.

21019999 is a modest number, since divided by 9999 gives 2101 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019993) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 253212 + ... + 253294.

It is an arithmetic number, because the mean of its divisors is an integer number (625632).

Almost surely, 2^21019999 is an apocalyptic number.

21019999 is a deficient number, since it is larger than the sum of its proper divisors (9010337).

21019999 is a wasteful number, since it uses less digits than its factorization.

21019999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148 (or 137 counting only the distinct ones).

The product of its (nonzero) digits is 13122, while the sum is 40.

The square root of 21019999 is about 4584.7572454820. The cubic root of 21019999 is about 275.9799703661.

It can be divided in two parts, 2101 and 9999, that added together give a square (12100 = 110²).

The spelling of 21019999 in words is "twenty-one million, nineteen thousand, nine hundred ninety-nine".