19961531 has 4 divisors (see below), whose sum is σ = 19971000. Its totient is φ = 19952064.

The previous prime is 19961527. The next prime is 19961567. The reversal of 19961531 is 13516991.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 13516991 = 127 ⋅106433.

It is a cyclic number.

It is not a de Polignac number, because 19961531 - 2² = 19961527 is a prime.

It is a super-2 number, since 2×19961531² = 796925439727922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19961491 and 19961500.

It is not an unprimeable number, because it can be changed into a prime (19961581) 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 in 3 ways as a sum of consecutive naturals, for example, 20 + ... + 6318.

It is an arithmetic number, because the mean of its divisors is an integer number (4992750).

Almost surely, 2^19961531 is an apocalyptic number.

19961531 is a deficient number, since it is larger than the sum of its proper divisors (9469).

19961531 is an equidigital number, since it uses as much as digits as its factorization.

19961531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9468.

The product of its digits is 7290, while the sum is 35.

The square root of 19961531 is about 4467.8329198841. The cubic root of 19961531 is about 271.2676150721.

The spelling of 19961531 in words is "nineteen million, nine hundred sixty-one thousand, five hundred thirty-one".