1990077821 has 2 divisors, whose sum is σ = 1990077822. Its totient is φ = 1990077820.

The previous prime is 1990077799. The next prime is 1990077827. The reversal of 1990077821 is 1287700991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1194048025 + 796029796 = 34555^2 + 28214^2 .

It is an emirp because it is prime and its reverse (1287700991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1990077821 - 2²² = 1985883517 is a prime.

It is a super-2 number, since 2×1990077821² = 7920819467272216082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1990077827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995038910 + 995038911.

It is an arithmetic number, because the mean of its divisors is an integer number (995038911).

Almost surely, 2^1990077821 is an apocalyptic number.

It is an amenable number.

1990077821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1990077821 is an equidigital number, since it uses as much as digits as its factorization.

1990077821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63504, while the sum is 44.

The square root of 1990077821 is about 44610.2882864480. The cubic root of 1990077821 is about 1257.8340678151.

The spelling of 1990077821 in words is "one billion, nine hundred ninety million, seventy-seven thousand, eight hundred twenty-one".