21400557 has 16 divisors (see below), whose sum is σ = 30412800. Its totient is φ = 13354352.

The previous prime is 21400523. The next prime is 21400583. The reversal of 21400557 is 75500412.

It is not a de Polignac number, because 21400557 - 2⁶ = 21400493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21400507) 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, 57 + ... + 6542.

It is an arithmetic number, because the mean of its divisors is an integer number (1900800).

Almost surely, 2^21400557 is an apocalyptic number.

It is an amenable number.

21400557 is a deficient number, since it is larger than the sum of its proper divisors (9012243).

21400557 is a wasteful number, since it uses less digits than its factorization.

21400557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6672.

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21400557 is about 4626.0736051213. The cubic root of 21400557 is about 277.6355185820.

Adding to 21400557 its reverse (75500412), we get a palindrome (96900969).

The spelling of 21400557 in words is "twenty-one million, four hundred thousand, five hundred fifty-seven".