61640399 has 4 divisors (see below), whose sum is σ = 63765960. Its totient is φ = 59514840.

The previous prime is 61640393. The next prime is 61640407. The reversal of 61640399 is 99304616.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 61640399 - 2¹² = 61636303 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 (61640393) 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, 1062737 + ... + 1062794.

It is an arithmetic number, because the mean of its divisors is an integer number (15941490).

Almost surely, 2^61640399 is an apocalyptic number.

61640399 is a deficient number, since it is larger than the sum of its proper divisors (2125561).

61640399 is a wasteful number, since it uses less digits than its factorization.

61640399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2125560.

The product of its (nonzero) digits is 34992, while the sum is 38.

The square root of 61640399 is about 7851.1399809200. The cubic root of 61640399 is about 395.0224822967.

The spelling of 61640399 in words is "sixty-one million, six hundred forty thousand, three hundred ninety-nine".