20129491 has 4 divisors (see below), whose sum is σ = 20144232. Its totient is φ = 20114752.

The previous prime is 20129471. The next prime is 20129497. The reversal of 20129491 is 19492102.

It is a happy number.

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 20129491 - 2⁷ = 20129363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20129497) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5086 + ... + 8131.

It is an arithmetic number, because the mean of its divisors is an integer number (5036058).

Almost surely, 2^20129491 is an apocalyptic number.

20129491 is a deficient number, since it is larger than the sum of its proper divisors (14741).

20129491 is a wasteful number, since it uses less digits than its factorization.

20129491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14740.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 20129491 is about 4486.5901306003. The cubic root of 20129491 is about 272.0263229643.

It can be divided in two parts, 201 and 29491, that added together give a palindrome (29692).

The spelling of 20129491 in words is "twenty million, one hundred twenty-nine thousand, four hundred ninety-one".