1900021 has 4 divisors (see below), whose sum is σ = 1961344. Its totient is φ = 1838700.

The previous prime is 1900009. The next prime is 1900037. The reversal of 1900021 is 1200091.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1200091 = 131 ⋅9161.

It is a cyclic number.

It is not a de Polignac number, because 1900021 - 2⁹ = 1899509 is a prime.

It is a super-2 number, since 2×1900021² = 7220159600882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1899974 and 1900010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1900121) 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, 30615 + ... + 30676.

It is an arithmetic number, because the mean of its divisors is an integer number (490336).

2^1900021 is an apocalyptic number.

It is an amenable number.

1900021 is a deficient number, since it is larger than the sum of its proper divisors (61323).

1900021 is an equidigital number, since it uses as much as digits as its factorization.

1900021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61322.

The product of its (nonzero) digits is 18, while the sum is 13.

The square root of 1900021 is about 1378.4124926886. The cubic root of 1900021 is about 123.8566892738.

The spelling of 1900021 in words is "one million, nine hundred thousand, twenty-one".