21125397 has 16 divisors (see below), whose sum is σ = 30061760. Its totient is φ = 13156992.

The previous prime is 21125393. The next prime is 21125443. The reversal of 21125397 is 79352112.

It is not a de Polignac number, because 21125397 - 2² = 21125393 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 (21125393) 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, 1623 + ... + 6699.

It is an arithmetic number, because the mean of its divisors is an integer number (1878860).

Almost surely, 2^21125397 is an apocalyptic number.

It is an amenable number.

21125397 is a deficient number, since it is larger than the sum of its proper divisors (8936363).

21125397 is a wasteful number, since it uses less digits than its factorization.

21125397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5172.

The product of its digits is 3780, while the sum is 30.

The square root of 21125397 is about 4596.2372654161. The cubic root of 21125397 is about 276.4404723682.

The spelling of 21125397 in words is "twenty-one million, one hundred twenty-five thousand, three hundred ninety-seven".