39897991 has 4 divisors (see below), whose sum is σ = 45597712. Its totient is φ = 34198272.

The previous prime is 39897989. The next prime is 39898003. The reversal of 39897991 is 19979893.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19979893 = 23 ⋅868691.

It is a cyclic number.

It is not a de Polignac number, because 39897991 - 2¹ = 39897989 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 (39897911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2849850 + ... + 2849863.

It is an arithmetic number, because the mean of its divisors is an integer number (11399428).

Almost surely, 2^39897991 is an apocalyptic number.

39897991 is a deficient number, since it is larger than the sum of its proper divisors (5699721).

39897991 is an equidigital number, since it uses as much as digits as its factorization.

39897991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5699720.

The product of its digits is 1102248, while the sum is 55.

The square root of 39897991 is about 6316.4856526394. The cubic root of 39897991 is about 341.7042202889.

It can be divided in two parts, 398 and 97991, that added together give a palindrome (98389).

The spelling of 39897991 in words is "thirty-nine million, eight hundred ninety-seven thousand, nine hundred ninety-one".