990138637 has 4 divisors (see below), whose sum is σ = 992751520. Its totient is φ = 987525756.

The previous prime is 990138631. The next prime is 990138673. The reversal of 990138637 is 736831099.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 990138637 - 2²⁷ = 855920909 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 (990138631) 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, 1305873 + ... + 1306630.

It is an arithmetic number, because the mean of its divisors is an integer number (248187880).

Almost surely, 2^990138637 is an apocalyptic number.

It is an amenable number.

990138637 is a deficient number, since it is larger than the sum of its proper divisors (2612883).

990138637 is a wasteful number, since it uses less digits than its factorization.

990138637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2612882.

The product of its (nonzero) digits is 244944, while the sum is 46.

The square root of 990138637 is about 31466.4684545311. The cubic root of 990138637 is about 996.7020142471.

The spelling of 990138637 in words is "nine hundred ninety million, one hundred thirty-eight thousand, six hundred thirty-seven".