19945021 has 4 divisors (see below), whose sum is σ = 19961632. Its totient is φ = 19928412.

The previous prime is 19945019. The next prime is 19945027. The reversal of 19945021 is 12054991.

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 19945021 - 2¹ = 19945019 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 (19945027) 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, 6351 + ... + 8956.

It is an arithmetic number, because the mean of its divisors is an integer number (4990408).

Almost surely, 2^19945021 is an apocalyptic number.

It is an amenable number.

19945021 is a deficient number, since it is larger than the sum of its proper divisors (16611).

19945021 is a wasteful number, since it uses less digits than its factorization.

19945021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16610.

The product of its (nonzero) digits is 3240, while the sum is 31.

The square root of 19945021 is about 4465.9848857783. The cubic root of 19945021 is about 271.1928067882.

The spelling of 19945021 in words is "nineteen million, nine hundred forty-five thousand, twenty-one".