212137721 has 2 divisors, whose sum is σ = 212137722. Its totient is φ = 212137720.

The previous prime is 212137703. The next prime is 212137727. The reversal of 212137721 is 127731212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 203376121 + 8761600 = 14261^2 + 2960^2 .

It is a cyclic number.

It is not a de Polignac number, because 212137721 - 2⁶ = 212137657 is a prime.

It is not a weakly prime, because it can be changed into another prime (212137727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106068860 + 106068861.

It is an arithmetic number, because the mean of its divisors is an integer number (106068861).

Almost surely, 2^212137721 is an apocalyptic number.

It is an amenable number.

212137721 is a deficient number, since it is larger than the sum of its proper divisors (1).

212137721 is an equidigital number, since it uses as much as digits as its factorization.

212137721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1176, while the sum is 26.

The square root of 212137721 is about 14564.9483692871. The cubic root of 212137721 is about 596.4022862852.

Adding to 212137721 its reverse (127731212), we get a palindrome (339868933).

The spelling of 212137721 in words is "two hundred twelve million, one hundred thirty-seven thousand, seven hundred twenty-one".