21949919 has 4 divisors (see below), whose sum is σ = 21967344. Its totient is φ = 21932496.

The previous prime is 21949877. The next prime is 21949927. The reversal of 21949919 is 91994912.

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 21949919 - 2⁸ = 21949663 is a prime.

It is a super-2 number, since 2×21949919² = 963597888213122, 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 21949919.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21949969) 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, 6662 + ... + 9395.

It is an arithmetic number, because the mean of its divisors is an integer number (5491836).

Almost surely, 2^21949919 is an apocalyptic number.

21949919 is a deficient number, since it is larger than the sum of its proper divisors (17425).

21949919 is a wasteful number, since it uses less digits than its factorization.

21949919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17424.

The product of its digits is 52488, while the sum is 44.

The square root of 21949919 is about 4685.0740655832. The cubic root of 21949919 is about 279.9911519313.

The spelling of 21949919 in words is "twenty-one million, nine hundred forty-nine thousand, nine hundred nineteen".