20515531 has 2 divisors, whose sum is σ = 20515532. Its totient is φ = 20515530.

The previous prime is 20515511. The next prime is 20515553. The reversal of 20515531 is 13551502.

It is an a-pointer prime, because the next prime (20515553) can be obtained adding 20515531 to its sum of digits (22).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20515531 - 2¹⁹ = 19991243 is a prime.

It is a super-2 number, since 2×20515531² = 841774024423922, which contains 22 as substring.

It is a Chen prime.

It is equal to p_1301179 and since 20515531 and 1301179 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (20515511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10257765 + 10257766.

It is an arithmetic number, because the mean of its divisors is an integer number (10257766).

Almost surely, 2^20515531 is an apocalyptic number.

20515531 is a deficient number, since it is larger than the sum of its proper divisors (1).

20515531 is an equidigital number, since it uses as much as digits as its factorization.

20515531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 750, while the sum is 22.

The square root of 20515531 is about 4529.4073563768. The cubic root of 20515531 is about 273.7542818148.

The spelling of 20515531 in words is "twenty million, five hundred fifteen thousand, five hundred thirty-one".