21698819 has 4 divisors (see below), whose sum is σ = 22160544. Its totient is φ = 21237096.

The previous prime is 21698801. The next prime is 21698827. The reversal of 21698819 is 91889612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21698819 - 2⁸ = 21698563 is a prime.

It is a super-2 number, since 2×21698819² = 941677491989522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21698819.

It is not an unprimeable number, because it can be changed into a prime (21698849) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 230792 + ... + 230885.

It is an arithmetic number, because the mean of its divisors is an integer number (5540136).

Almost surely, 2^21698819 is an apocalyptic number.

21698819 is a deficient number, since it is larger than the sum of its proper divisors (461725).

21698819 is an equidigital number, since it uses as much as digits as its factorization.

21698819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 461724.

The product of its digits is 62208, while the sum is 44.

The square root of 21698819 is about 4658.1991155381. The cubic root of 21698819 is about 278.9193850758.

The spelling of 21698819 in words is "twenty-one million, six hundred ninety-eight thousand, eight hundred nineteen".