1691254121 has 4 divisors (see below), whose sum is σ = 1691366544. Its totient is φ = 1691141700.

The previous prime is 1691254111. The next prime is 1691254139. The reversal of 1691254121 is 1214521961.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1691254121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1691254111) 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, 29375 + ... + 65156.

It is an arithmetic number, because the mean of its divisors is an integer number (422841636).

Almost surely, 2^1691254121 is an apocalyptic number.

It is an amenable number.

1691254121 is a deficient number, since it is larger than the sum of its proper divisors (112423).

1691254121 is an equidigital number, since it uses as much as digits as its factorization.

1691254121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112422.

The product of its digits is 4320, while the sum is 32.

The square root of 1691254121 is about 41124.8601335008. The cubic root of 1691254121 is about 1191.4329937071.

The spelling of 1691254121 in words is "one billion, six hundred ninety-one million, two hundred fifty-four thousand, one hundred twenty-one".