20415491 has 2 divisors, whose sum is σ = 20415492. Its totient is φ = 20415490.

The previous prime is 20415469. The next prime is 20415509. The reversal of 20415491 is 19451402.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20415491 is a prime.

It is a Sophie Germain prime.

It is equal to p_1295252 and since 20415491 and 1295252 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20415491.

It is not a weakly prime, because it can be changed into another prime (20415401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10207745 + 10207746.

It is an arithmetic number, because the mean of its divisors is an integer number (10207746).

Almost surely, 2^20415491 is an apocalyptic number.

20415491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20415491 is an equidigital number, since it uses as much as digits as its factorization.

20415491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 20415491 is about 4518.3504733475. The cubic root of 20415491 is about 273.3085867278.

Adding to 20415491 its reverse (19451402), we get a palindrome (39866893).

The spelling of 20415491 in words is "twenty million, four hundred fifteen thousand, four hundred ninety-one".