21992091 has 8 divisors (see below), whose sum is σ = 31988544. Its totient is φ = 13328520.

The previous prime is 21992083. The next prime is 21992129. The reversal of 21992091 is 19029912.

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

It is not a de Polignac number, because 21992091 - 2³ = 21992083 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33), and also a Moran number because the ratio is a prime number: 666427 = 21992091 / (2 + 1 + 9 + 9 + 2 + 0 + 9 + 1).

It is not an unprimeable number, because it can be changed into a prime (21992021) 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, 333181 + ... + 333246.

It is an arithmetic number, because the mean of its divisors is an integer number (3998568).

Almost surely, 2^21992091 is an apocalyptic number.

21992091 is a deficient number, since it is larger than the sum of its proper divisors (9996453).

21992091 is a wasteful number, since it uses less digits than its factorization.

21992091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 666441.

The product of its (nonzero) digits is 2916, while the sum is 33.

The square root of 21992091 is about 4689.5725818032. The cubic root of 21992091 is about 280.1703512697.

The spelling of 21992091 in words is "twenty-one million, nine hundred ninety-two thousand, ninety-one".