1990621 has 2 divisors, whose sum is σ = 1990622. Its totient is φ = 1990620.

The previous prime is 1990607. The next prime is 1990643. The reversal of 1990621 is 1260991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1125721 + 864900 = 1061^2 + 930^2 .

It is an emirp because it is prime and its reverse (1260991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1990621 - 2⁷ = 1990493 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1990621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1990661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995310 + 995311.

It is an arithmetic number, because the mean of its divisors is an integer number (995311).

2^1990621 is an apocalyptic number.

It is an amenable number.

1990621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1990621 is an equidigital number, since it uses as much as digits as its factorization.

1990621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 1990621 is about 1410.8936884117. The cubic root of 1990621 is about 125.7948496657.

The spelling of 1990621 in words is "one million, nine hundred ninety thousand, six hundred twenty-one".