61991664 has 60 divisors (see below), whose sum is σ = 186298344. Its totient is φ = 17711232.

The previous prime is 61991663. The next prime is 61991669. The reversal of 61991664 is 46619916.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61991663) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10827 + ... + 15530.

Almost surely, 2^61991664 is an apocalyptic number.

It is an amenable number.

61991664 is an abundant number, since it is smaller than the sum of its proper divisors (124306680).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

61991664 is a wasteful number, since it uses less digits than its factorization.

61991664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26382 (or 26369 counting only the distinct ones).

The product of its digits is 69984, while the sum is 42.

The square root of 61991664 is about 7873.4785196887. The cubic root of 61991664 is about 395.7714220093.

The spelling of 61991664 in words is "sixty-one million, nine hundred ninety-one thousand, six hundred sixty-four".