1961555021 has 2 divisors, whose sum is σ = 1961555022. Its totient is φ = 1961555020.

The previous prime is 1961554999. The next prime is 1961555033. The reversal of 1961555021 is 1205551691.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1870562500 + 90992521 = 43250^2 + 9539^2 .

It is a cyclic number.

It is not a de Polignac number, because 1961555021 - 2⁶ = 1961554957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1961555221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 980777510 + 980777511.

It is an arithmetic number, because the mean of its divisors is an integer number (980777511).

Almost surely, 2^1961555021 is an apocalyptic number.

It is an amenable number.

1961555021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1961555021 is an equidigital number, since it uses as much as digits as its factorization.

1961555021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13500, while the sum is 35.

The square root of 1961555021 is about 44289.4459324115. The cubic root of 1961555021 is about 1251.7958232595.

The spelling of 1961555021 in words is "one billion, nine hundred sixty-one million, five hundred fifty-five thousand, twenty-one".