66156421 has 2 divisors, whose sum is σ = 66156422. Its totient is φ = 66156420.

The previous prime is 66156383. The next prime is 66156427. The reversal of 66156421 is 12465166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54967396 + 11189025 = 7414^2 + 3345^2 .

It is a cyclic number.

It is not a de Polignac number, because 66156421 - 2¹⁵ = 66123653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66156427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33078210 + 33078211.

It is an arithmetic number, because the mean of its divisors is an integer number (33078211).

Almost surely, 2^66156421 is an apocalyptic number.

It is an amenable number.

66156421 is a deficient number, since it is larger than the sum of its proper divisors (1).

66156421 is an equidigital number, since it uses as much as digits as its factorization.

66156421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 31.

The square root of 66156421 is about 8133.6597543787. The cubic root of 66156421 is about 404.4430101794.

The spelling of 66156421 in words is "sixty-six million, one hundred fifty-six thousand, four hundred twenty-one".