20986531 has 2 divisors, whose sum is σ = 20986532. Its totient is φ = 20986530.

The previous prime is 20986529. The next prime is 20986561. The reversal of 20986531 is 13568902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20986531 - 2¹ = 20986529 is a prime.

It is a super-2 number, since 2×20986531² = 880868966827922, which contains 22 as substring.

Together with 20986529, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20986561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10493265 + 10493266.

It is an arithmetic number, because the mean of its divisors is an integer number (10493266).

Almost surely, 2^20986531 is an apocalyptic number.

20986531 is a deficient number, since it is larger than the sum of its proper divisors (1).

20986531 is an equidigital number, since it uses as much as digits as its factorization.

20986531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 20986531 is about 4581.1058708569. The cubic root of 20986531 is about 275.8334209760.

The spelling of 20986531 in words is "twenty million, nine hundred eighty-six thousand, five hundred thirty-one".