1025640021 has 24 divisors (see below), whose sum is σ = 1599075264. Its totient is φ = 583027200.

The previous prime is 1025640017. The next prime is 1025640041. The reversal of 1025640021 is 1200465201.

It is not a de Polignac number, because 1025640021 - 2² = 1025640017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1025640021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1025640001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10296 + ... + 46446.

It is an arithmetic number, because the mean of its divisors is an integer number (66628136).

Almost surely, 2^1025640021 is an apocalyptic number.

It is an amenable number.

1025640021 is a deficient number, since it is larger than the sum of its proper divisors (573435243).

1025640021 is a wasteful number, since it uses less digits than its factorization.

1025640021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36361 (or 36354 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 1025640021 is about 32025.6150760606. The cubic root of 1025640021 is about 1008.4746510735.

The spelling of 1025640021 in words is "one billion, twenty-five million, six hundred forty thousand, twenty-one".