19678021 has 4 divisors (see below), whose sum is σ = 21466944. Its totient is φ = 17889100.

The previous prime is 19678019. The next prime is 19678033. The reversal of 19678021 is 12087691.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19678021 - 2¹ = 19678019 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19678081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 894445 + ... + 894466.

It is an arithmetic number, because the mean of its divisors is an integer number (5366736).

Almost surely, 2^19678021 is an apocalyptic number.

19678021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19678021 is a deficient number, since it is larger than the sum of its proper divisors (1788923).

19678021 is a wasteful number, since it uses less digits than its factorization.

19678021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1788922.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 19678021 is about 4435.9915464302. The cubic root of 19678021 is about 269.9772317335.

The spelling of 19678021 in words is "nineteen million, six hundred seventy-eight thousand, twenty-one".