21620091 has 4 divisors (see below), whose sum is σ = 28826792. Its totient is φ = 14413392.

The previous prime is 21620087. The next prime is 21620101. The reversal of 21620091 is 19002612.

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

It is not a de Polignac number, because 21620091 - 2² = 21620087 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21620021) 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, 3603346 + ... + 3603351.

It is an arithmetic number, because the mean of its divisors is an integer number (7206698).

Almost surely, 2^21620091 is an apocalyptic number.

21620091 is a deficient number, since it is larger than the sum of its proper divisors (7206701).

21620091 is an equidigital number, since it uses as much as digits as its factorization.

21620091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7206700.

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 21620091 is about 4649.7409605267. The cubic root of 21620091 is about 278.5816497048.

The spelling of 21620091 in words is "twenty-one million, six hundred twenty thousand, ninety-one".