19911957 has 16 divisors (see below), whose sum is σ = 29366400. Its totient is φ = 11921472.

The previous prime is 19911953. The next prime is 19911959. The reversal of 19911957 is 75911991.

It is a happy number.

It is not a de Polignac number, because 19911957 - 2² = 19911953 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19911953) 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, 5457 + ... + 8342.

It is an arithmetic number, because the mean of its divisors is an integer number (1835400).

Almost surely, 2^19911957 is an apocalyptic number.

It is an amenable number.

19911957 is a deficient number, since it is larger than the sum of its proper divisors (9454443).

19911957 is a wasteful number, since it uses less digits than its factorization.

19911957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13852.

The product of its digits is 25515, while the sum is 42.

The square root of 19911957 is about 4462.2815912939. The cubic root of 19911957 is about 271.0428666367.

The spelling of 19911957 in words is "nineteen million, nine hundred eleven thousand, nine hundred fifty-seven".