19951640 has 16 divisors (see below), whose sum is σ = 44891280. Its totient is φ = 7980640.

The previous prime is 19951637. The next prime is 19951661. The reversal of 19951640 is 4615991.

It is a self number, because there is not a number n which added to its sum of digits gives 19951640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 249356 + ... + 249435.

It is an arithmetic number, because the mean of its divisors is an integer number (2805705).

Almost surely, 2^19951640 is an apocalyptic number.

19951640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19951640 is an abundant number, since it is smaller than the sum of its proper divisors (24939640).

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

19951640 is a wasteful number, since it uses less digits than its factorization.

19951640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498802 (or 498798 counting only the distinct ones).

The product of its (nonzero) digits is 9720, while the sum is 35.

The square root of 19951640 is about 4466.7258702544. The cubic root of 19951640 is about 271.2228030240. Note that the first 3 decimals are identical.

The spelling of 19951640 in words is "nineteen million, nine hundred fifty-one thousand, six hundred forty".