212139661 has 2 divisors, whose sum is σ = 212139662. Its totient is φ = 212139660.

The previous prime is 212139637. The next prime is 212139667. The reversal of 212139661 is 166931212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 210685225 + 1454436 = 14515^2 + 1206^2 .

It is a cyclic number.

It is not a de Polignac number, because 212139661 - 2²⁷ = 77921933 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (212139667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106069830 + 106069831.

It is an arithmetic number, because the mean of its divisors is an integer number (106069831).

Almost surely, 2^212139661 is an apocalyptic number.

It is an amenable number.

212139661 is a deficient number, since it is larger than the sum of its proper divisors (1).

212139661 is an equidigital number, since it uses as much as digits as its factorization.

212139661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 31.

The square root of 212139661 is about 14565.0149673799. The cubic root of 212139661 is about 596.4041043131.

The spelling of 212139661 in words is "two hundred twelve million, one hundred thirty-nine thousand, six hundred sixty-one".