1691397431 has 4 divisors (see below), whose sum is σ = 1691484312. Its totient is φ = 1691310552.

The previous prime is 1691397401. The next prime is 1691397457. The reversal of 1691397431 is 1347931961.

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: 1347931961 = 101 ⋅13345861.

It is a cyclic number.

It is not a de Polignac number, because 1691397431 - 2¹⁰ = 1691396407 is a prime.

It is a super-2 number, since 2×1691397431² = 5721650539186799522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1691397401) 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, 740 + ... + 58166.

It is an arithmetic number, because the mean of its divisors is an integer number (422871078).

Almost surely, 2^1691397431 is an apocalyptic number.

1691397431 is a deficient number, since it is larger than the sum of its proper divisors (86881).

1691397431 is an equidigital number, since it uses as much as digits as its factorization.

1691397431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86880.

The product of its digits is 122472, while the sum is 44.

The square root of 1691397431 is about 41126.6024733383. The cubic root of 1691397431 is about 1191.4666451531.

The spelling of 1691397431 in words is "one billion, six hundred ninety-one million, three hundred ninety-seven thousand, four hundred thirty-one".