20991149 has 2 divisors, whose sum is σ = 20991150. Its totient is φ = 20991148.

The previous prime is 20991121. The next prime is 20991211. The reversal of 20991149 is 94119902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20475625 + 515524 = 4525^2 + 718^2 .

It is a cyclic number.

It is not a de Polignac number, because 20991149 - 2¹⁶ = 20925613 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20991049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10495574 + 10495575.

It is an arithmetic number, because the mean of its divisors is an integer number (10495575).

Almost surely, 2^20991149 is an apocalyptic number.

It is an amenable number.

20991149 is a deficient number, since it is larger than the sum of its proper divisors (1).

20991149 is an equidigital number, since it uses as much as digits as its factorization.

20991149 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 35.

The square root of 20991149 is about 4581.6098699038. The cubic root of 20991149 is about 275.8536514962.

The spelling of 20991149 in words is "twenty million, nine hundred ninety-one thousand, one hundred forty-nine".