21801919 has 4 divisors (see below), whose sum is σ = 21831040. Its totient is φ = 21772800.

The previous prime is 21801893. The next prime is 21801929. The reversal of 21801919 is 91910812.

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 21801919 - 2⁵ = 21801887 is a prime.

It is a super-2 number, since 2×21801919² = 950647344165122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21801929) 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, 13407 + ... + 14944.

It is an arithmetic number, because the mean of its divisors is an integer number (5457760).

Almost surely, 2^21801919 is an apocalyptic number.

21801919 is a deficient number, since it is larger than the sum of its proper divisors (29121).

21801919 is an equidigital number, since it uses as much as digits as its factorization.

21801919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29120.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 21801919 is about 4669.2525097707. The cubic root of 21801919 is about 279.3604407796.

The spelling of 21801919 in words is "twenty-one million, eight hundred one thousand, nine hundred nineteen".