21028819 has 8 divisors (see below), whose sum is σ = 24808448. Its totient is φ = 17443080.

The previous prime is 21028771. The next prime is 21028823. The reversal of 21028819 is 91882012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21028819 - 2¹³ = 21020627 is a prime.

It is a super-2 number, since 2×21028819² = 884422457069522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is not an unprimeable number, because it can be changed into a prime (21028619) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48237 + ... + 48670.

It is an arithmetic number, because the mean of its divisors is an integer number (3101056).

Almost surely, 2^21028819 is an apocalyptic number.

21028819 is a deficient number, since it is larger than the sum of its proper divisors (3779629).

21028819 is an equidigital number, since it uses as much as digits as its factorization.

21028819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96945.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 21028819 is about 4585.7190275899. The cubic root of 21028819 is about 276.0185654038.

The spelling of 21028819 in words is "twenty-one million, twenty-eight thousand, eight hundred nineteen".