71621991 has 24 divisors (see below), whose sum is σ = 120177824. Its totient is φ = 40253760.

The previous prime is 71621983. The next prime is 71621993. The reversal of 71621991 is 19912617.

It is not a de Polignac number, because 71621991 - 2³ = 71621983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71621993) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5476 + ... + 13161.

Almost surely, 2^71621991 is an apocalyptic number.

71621991 is a deficient number, since it is larger than the sum of its proper divisors (48555833).

71621991 is a wasteful number, since it uses less digits than its factorization.

71621991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18711 (or 18708 counting only the distinct ones).

The product of its digits is 6804, while the sum is 36.

The square root of 71621991 is about 8462.9776674643. The cubic root of 71621991 is about 415.2874400970.

The spelling of 71621991 in words is "seventy-one million, six hundred twenty-one thousand, nine hundred ninety-one".