20515381 has 2 divisors, whose sum is σ = 20515382. Its totient is φ = 20515380.

The previous prime is 20515367. The next prime is 20515393. The reversal of 20515381 is 18351502.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19096900 + 1418481 = 4370^2 + 1191^2 .

It is a cyclic number.

It is not a de Polignac number, because 20515381 - 2⁵ = 20515349 is a prime.

It is a super-2 number, since 2×20515381² = 841761715150322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20515351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10257690 + 10257691.

It is an arithmetic number, because the mean of its divisors is an integer number (10257691).

Almost surely, 2^20515381 is an apocalyptic number.

It is an amenable number.

20515381 is a deficient number, since it is larger than the sum of its proper divisors (1).

20515381 is an equidigital number, since it uses as much as digits as its factorization.

20515381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 20515381 is about 4529.3907978888. The cubic root of 20515381 is about 273.7536146253.

Adding to 20515381 its reverse (18351502), we get a palindrome (38866883).

The spelling of 20515381 in words is "twenty million, five hundred fifteen thousand, three hundred eighty-one".