20615531 has 2 divisors, whose sum is σ = 20615532. Its totient is φ = 20615530.

The previous prime is 20615503. The next prime is 20615537. The reversal of 20615531 is 13551602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20615531 - 2⁶ = 20615467 is a prime.

It is a super-2 number, since 2×20615531² = 850000236823922, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20615497 and 20615506.

It is not a weakly prime, because it can be changed into another prime (20615537) 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, 10307765 + 10307766.

It is an arithmetic number, because the mean of its divisors is an integer number (10307766).

Almost surely, 2^20615531 is an apocalyptic number.

20615531 is a deficient number, since it is larger than the sum of its proper divisors (1).

20615531 is an equidigital number, since it uses as much as digits as its factorization.

20615531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 20615531 is about 4540.4329088755. The cubic root of 20615531 is about 274.1983530089.

The spelling of 20615531 in words is "twenty million, six hundred fifteen thousand, five hundred thirty-one".