1990052021 has 4 divisors (see below), whose sum is σ = 1990167552. Its totient is φ = 1989936492.

The previous prime is 1990052017. The next prime is 1990052033. The reversal of 1990052021 is 1202500991.

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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1202500991 = 61 ⋅19713131.

It is a cyclic number.

It is not a de Polignac number, because 1990052021 - 2² = 1990052017 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 (1990052081) 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, 26165 + ... + 68298.

It is an arithmetic number, because the mean of its divisors is an integer number (497541888).

Almost surely, 2^1990052021 is an apocalyptic number.

It is an amenable number.

1990052021 is a deficient number, since it is larger than the sum of its proper divisors (115531).

1990052021 is an equidigital number, since it uses as much as digits as its factorization.

1990052021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115530.

The product of its (nonzero) digits is 1620, while the sum is 29.

The square root of 1990052021 is about 44609.9991145483. Note that the first 3 decimals coincide. The cubic root of 1990052021 is about 1257.8286321383.

The spelling of 1990052021 in words is "one billion, nine hundred ninety million, fifty-two thousand, twenty-one".