20402531 has 2 divisors, whose sum is σ = 20402532. Its totient is φ = 20402530.

The previous prime is 20402521. The next prime is 20402537. The reversal of 20402531 is 13520402.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20402531 - 2⁶ = 20402467 is a prime.

It is a super-2 number, since 2×20402531² = 832526542411922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20402537) 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 as a sum of consecutive naturals, namely, 10201265 + 10201266.

It is an arithmetic number, because the mean of its divisors is an integer number (10201266).

Almost surely, 2^20402531 is an apocalyptic number.

20402531 is a deficient number, since it is larger than the sum of its proper divisors (1).

20402531 is an equidigital number, since it uses as much as digits as its factorization.

20402531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 20402531 is about 4516.9160939739. The cubic root of 20402531 is about 273.2507412896.

Adding to 20402531 its reverse (13520402), we get a palindrome (33922933).

The spelling of 20402531 in words is "twenty million, four hundred two thousand, five hundred thirty-one".