1287655921 has 4 divisors (see below), whose sum is σ = 1297795072. Its totient is φ = 1277516772.

The previous prime is 1287655867. The next prime is 1287655937. The reversal of 1287655921 is 1295567821.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1295567821 = 491 ⋅2638631.

It is a cyclic number.

It is not a de Polignac number, because 1287655921 - 2⁷ = 1287655793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1287655961) 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, 5069385 + ... + 5069638.

It is an arithmetic number, because the mean of its divisors is an integer number (324448768).

Almost surely, 2^1287655921 is an apocalyptic number.

It is an amenable number.

1287655921 is a deficient number, since it is larger than the sum of its proper divisors (10139151).

1287655921 is a wasteful number, since it uses less digits than its factorization.

1287655921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10139150.

The product of its digits is 302400, while the sum is 46.

The square root of 1287655921 is about 35883.9228764080. The cubic root of 1287655921 is about 1087.9274707567.

The spelling of 1287655921 in words is "one billion, two hundred eighty-seven million, six hundred fifty-five thousand, nine hundred twenty-one".