1691469978 has 64 divisors (see below), whose sum is σ = 3929627520. Its totient is φ = 479692800.

The previous prime is 1691469953. The next prime is 1691470057. The reversal of 1691469978 is 8799641961.

It is a happy number.

It is a super-2 number, since 2×1691469978² = 5722141372950640968, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 198918 + ... + 207246.

It is an arithmetic number, because the mean of its divisors is an integer number (61400430).

Almost surely, 2^1691469978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1691469978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1964813760).

1691469978 is an abundant number, since it is smaller than the sum of its proper divisors (2238157542).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1691469978 is a wasteful number, since it uses less digits than its factorization.

1691469978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8543.

The product of its digits is 5878656, while the sum is 60.

The square root of 1691469978 is about 41127.4844599083. The cubic root of 1691469978 is about 1191.4836796070.

The spelling of 1691469978 in words is "one billion, six hundred ninety-one million, four hundred sixty-nine thousand, nine hundred seventy-eight".