21370557 has 24 divisors (see below), whose sum is σ = 31405728. Its totient is φ = 12916800.

The previous prime is 21370549. The next prime is 21370561. The reversal of 21370557 is 75507312.

It is not a de Polignac number, because 21370557 - 2³ = 21370549 is a prime.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21370537) 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, 30582 + ... + 31272.

It is an arithmetic number, because the mean of its divisors is an integer number (1308572).

Almost surely, 2^21370557 is an apocalyptic number.

It is an amenable number.

21370557 is a deficient number, since it is larger than the sum of its proper divisors (10035171).

21370557 is a wasteful number, since it uses less digits than its factorization.

21370557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 781 (or 768 counting only the distinct ones).

The product of its (nonzero) digits is 7350, while the sum is 30.

The square root of 21370557 is about 4622.8299774056. The cubic root of 21370557 is about 277.5057250665.

Adding to 21370557 its reverse (75507312), we get a palindrome (96877869).

The spelling of 21370557 in words is "twenty-one million, three hundred seventy thousand, five hundred fifty-seven".