1991664390 has 32 divisors (see below), whose sum is σ = 4783555296. Its totient is φ = 530714880.

The previous prime is 1991664377. The next prime is 1991664397. The reversal of 1991664390 is 934661991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991664397) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17394 + ... + 65466.

It is an arithmetic number, because the mean of its divisors is an integer number (149486103).

Almost surely, 2^1991664390 is an apocalyptic number.

1991664390 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1991664390 is an abundant number, since it is smaller than the sum of its proper divisors (2791890906).

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

1991664390 is a wasteful number, since it uses less digits than its factorization.

1991664390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49464.

The product of its (nonzero) digits is 314928, while the sum is 48.

The square root of 1991664390 is about 44628.0672895432. The cubic root of 1991664390 is about 1258.1682441001.

The spelling of 1991664390 in words is "one billion, nine hundred ninety-one million, six hundred sixty-four thousand, three hundred ninety".