20921091 has 16 divisors (see below), whose sum is σ = 28790784. Its totient is φ = 13505184.

The previous prime is 20921083. The next prime is 20921119. The reversal of 20921091 is 19012902.

It is not a de Polignac number, because 20921091 - 2³ = 20921083 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20921041) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15745 + ... + 17021.

It is an arithmetic number, because the mean of its divisors is an integer number (1799424).

Almost surely, 2^20921091 is an apocalyptic number.

20921091 is a deficient number, since it is larger than the sum of its proper divisors (7869693).

20921091 is a wasteful number, since it uses less digits than its factorization.

20921091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1450.

The product of its (nonzero) digits is 324, while the sum is 24.

The square root of 20921091 is about 4573.9579141046. The cubic root of 20921091 is about 275.5464220859.

Adding to 20921091 its reverse (19012902), we get a palindrome (39933993).

The spelling of 20921091 in words is "twenty million, nine hundred twenty-one thousand, ninety-one".