1687121639 has 4 divisors (see below), whose sum is σ = 1928139024. Its totient is φ = 1446104256.

The previous prime is 1687121629. The next prime is 1687121651. The reversal of 1687121639 is 9361217861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9361217861 = 4327 ⋅2163443.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1687121639 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1687121639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1687121609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 120508682 + ... + 120508695.

It is an arithmetic number, because the mean of its divisors is an integer number (482034756).

Almost surely, 2^1687121639 is an apocalyptic number.

1687121639 is a deficient number, since it is larger than the sum of its proper divisors (241017385).

1687121639 is an equidigital number, since it uses as much as digits as its factorization.

1687121639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241017384.

The product of its digits is 108864, while the sum is 44.

The square root of 1687121639 is about 41074.5862912824. The cubic root of 1687121639 is about 1190.4618029697.

The spelling of 1687121639 in words is "one billion, six hundred eighty-seven million, one hundred twenty-one thousand, six hundred thirty-nine".