66491639 has 2 divisors, whose sum is σ = 66491640. Its totient is φ = 66491638.

The previous prime is 66491609. The next prime is 66491651. The reversal of 66491639 is 93619466.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66491639 - 2¹⁶ = 66426103 is a prime.

It is a super-2 number, since 2×66491639² = 8842276113812642, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66491639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66491609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33245819 + 33245820.

It is an arithmetic number, because the mean of its divisors is an integer number (33245820).

Almost surely, 2^66491639 is an apocalyptic number.

66491639 is a deficient number, since it is larger than the sum of its proper divisors (1).

66491639 is an equidigital number, since it uses as much as digits as its factorization.

66491639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 209952, while the sum is 44.

The square root of 66491639 is about 8154.2405532336. The cubic root of 66491639 is about 405.1249708328.

The spelling of 66491639 in words is "sixty-six million, four hundred ninety-one thousand, six hundred thirty-nine".