61671991 has 2 divisors, whose sum is σ = 61671992. Its totient is φ = 61671990.

The previous prime is 61671983. The next prime is 61672027. The reversal of 61671991 is 19917616.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 61671991 - 2³ = 61671983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61671941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30835995 + 30835996.

It is an arithmetic number, because the mean of its divisors is an integer number (30835996).

Almost surely, 2^61671991 is an apocalyptic number.

61671991 is a deficient number, since it is larger than the sum of its proper divisors (1).

61671991 is an equidigital number, since it uses as much as digits as its factorization.

61671991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20412, while the sum is 40.

The square root of 61671991 is about 7853.1516603208. The cubic root of 61671991 is about 395.0899565455.

The spelling of 61671991 in words is "sixty-one million, six hundred seventy-one thousand, nine hundred ninety-one".