21819998 has 4 divisors (see below), whose sum is σ = 32730000. Its totient is φ = 10909998.

The previous prime is 21819991. The next prime is 21820013. The reversal of 21819998 is 89991812.

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

It is a super-2 number, since 2×21819998² = 952224625440008, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21819991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5454998 + ... + 5455001.

It is an arithmetic number, because the mean of its divisors is an integer number (8182500).

Almost surely, 2^21819998 is an apocalyptic number.

21819998 is a deficient number, since it is larger than the sum of its proper divisors (10910002).

21819998 is a wasteful number, since it uses less digits than its factorization.

21819998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10910001.

The product of its digits is 93312, while the sum is 47.

The square root of 21819998 is about 4671.1880715724. The cubic root of 21819998 is about 279.4376382962.

The spelling of 21819998 in words is "twenty-one million, eight hundred nineteen thousand, nine hundred ninety-eight".