191720400 has 120 divisors (see below), whose sum is σ = 618022944. Its totient is φ = 50803200.

The previous prime is 191720371. The next prime is 191720401. The reversal of 191720400 is 4027191.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191720401) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 235995 + ... + 236805.

Almost surely, 2^191720400 is an apocalyptic number.

191720400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 191720400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (309011472).

191720400 is an abundant number, since it is smaller than the sum of its proper divisors (426302544).

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

191720400 is a wasteful number, since it uses less digits than its factorization.

191720400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1029 (or 1018 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 191720400 is about 13846.3135888221. The cubic root of 191720400 is about 576.6196552868.

Adding to 191720400 its reverse (4027191), we get a palindrome (195747591).

The spelling of 191720400 in words is "one hundred ninety-one million, seven hundred twenty thousand, four hundred".