20420531 has 2 divisors, whose sum is σ = 20420532. Its totient is φ = 20420530.

The previous prime is 20420503. The next prime is 20420557. The reversal of 20420531 is 13502402.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20420531 is a prime.

It is a super-2 number, since 2×20420531² = 833996172643922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20420591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10210265 + 10210266.

It is an arithmetic number, because the mean of its divisors is an integer number (10210266).

Almost surely, 2^20420531 is an apocalyptic number.

20420531 is a deficient number, since it is larger than the sum of its proper divisors (1).

20420531 is an equidigital number, since it uses as much as digits as its factorization.

20420531 is an evil number, because the sum of its binary digits is even.

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

The square root of 20420531 is about 4518.9081645902. The cubic root of 20420531 is about 273.3310755647.

Adding to 20420531 its reverse (13502402), we get a palindrome (33922933).

The spelling of 20420531 in words is "twenty million, four hundred twenty thousand, five hundred thirty-one".