20871491 has 2 divisors, whose sum is σ = 20871492. Its totient is φ = 20871490.

The previous prime is 20871449. The next prime is 20871497. The reversal of 20871491 is 19417802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20871491 - 2¹⁰ = 20870467 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20871497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10435745 + 10435746.

It is an arithmetic number, because the mean of its divisors is an integer number (10435746).

Almost surely, 2^20871491 is an apocalyptic number.

20871491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20871491 is an equidigital number, since it uses as much as digits as its factorization.

20871491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 20871491 is about 4568.5326966106. The cubic root of 20871491 is about 275.3284934018.

The spelling of 20871491 in words is "twenty million, eight hundred seventy-one thousand, four hundred ninety-one".