661138497 has 16 divisors (see below), whose sum is σ = 1031016000. Its totient is φ = 417560832.

The previous prime is 661138487. The next prime is 661138523. The reversal of 661138497 is 794831166.

It is a happy number.

It is not a de Polignac number, because 661138497 - 2⁴ = 661138481 is a prime.

It is a super-2 number, since 2×661138497² = 874208224430838018, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661138487) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 643872 + ... + 644897.

It is an arithmetic number, because the mean of its divisors is an integer number (64438500).

Almost surely, 2^661138497 is an apocalyptic number.

It is an amenable number.

661138497 is a deficient number, since it is larger than the sum of its proper divisors (369877503).

661138497 is a wasteful number, since it uses less digits than its factorization.

661138497 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1288797 (or 1288791 counting only the distinct ones).

The product of its digits is 217728, while the sum is 45.

The square root of 661138497 is about 25712.6135777754. The cubic root of 661138497 is about 871.1591090059.

The spelling of 661138497 in words is "six hundred sixty-one million, one hundred thirty-eight thousand, four hundred ninety-seven".