20121531 has 4 divisors (see below), whose sum is σ = 26828712. Its totient is φ = 13414352.

The previous prime is 20121467. The next prime is 20121533. The reversal of 20121531 is 13512102.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20121531 - 2⁶ = 20121467 is a prime.

It is a super-2 number, since 2×20121531² = 809752019567922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20121531.

It is not an unprimeable number, because it can be changed into a prime (20121533) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3353586 + ... + 3353591.

It is an arithmetic number, because the mean of its divisors is an integer number (6707178).

Almost surely, 2^20121531 is an apocalyptic number.

20121531 is a deficient number, since it is larger than the sum of its proper divisors (6707181).

20121531 is an equidigital number, since it uses as much as digits as its factorization.

20121531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6707180.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 20121531 is about 4485.7029549447. The cubic root of 20121531 is about 271.9904615672.

Adding to 20121531 its reverse (13512102), we get a palindrome (33633633).

The spelling of 20121531 in words is "twenty million, one hundred twenty-one thousand, five hundred thirty-one".