19916391 has 16 divisors (see below), whose sum is σ = 29587968. Its totient is φ = 11812800.

The previous prime is 19916387. The next prime is 19916399. The reversal of 19916391 is 19361991.

19916391 = 413² + 414² + ... + 506².

It is a happy number.

It is not a de Polignac number, because 19916391 - 2² = 19916387 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19916399) 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, 4870 + ... + 7971.

It is an arithmetic number, because the mean of its divisors is an integer number (1849248).

Almost surely, 2^19916391 is an apocalyptic number.

19916391 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

19916391 is a deficient number, since it is larger than the sum of its proper divisors (9671577).

19916391 is a wasteful number, since it uses less digits than its factorization.

19916391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12902.

The product of its digits is 13122, while the sum is 39.

The square root of 19916391 is about 4462.7783946775. The cubic root of 19916391 is about 271.0629837766.

The spelling of 19916391 in words is "nineteen million, nine hundred sixteen thousand, three hundred ninety-one".