19991550 has 24 divisors (see below), whose sum is σ = 49579416. Its totient is φ = 5331040.

The previous prime is 19991549. The next prime is 19991551. The reversal of 19991550 is 5519991.

It is an interprime number because it is at equal distance from previous prime (19991549) and next prime (19991551).

It is a junction number, because it is equal to n+sod(n) for n = 19991499 and 19991508.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19991551) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 66489 + ... + 66788.

It is an arithmetic number, because the mean of its divisors is an integer number (2065809).

Almost surely, 2^19991550 is an apocalyptic number.

19991550 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

19991550 is an abundant number, since it is smaller than the sum of its proper divisors (29587866).

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

19991550 is a wasteful number, since it uses less digits than its factorization.

19991550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133292 (or 133287 counting only the distinct ones).

The product of its (nonzero) digits is 18225, while the sum is 39.

The square root of 19991550 is about 4471.1911164700. The cubic root of 19991550 is about 271.4035282263.

The spelling of 19991550 in words is "nineteen million, nine hundred ninety-one thousand, five hundred fifty".