21101657 has 4 divisors (see below), whose sum is σ = 21113856. Its totient is φ = 21089460.

The previous prime is 21101651. The next prime is 21101677. The reversal of 21101657 is 75610112.

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.

It is a cyclic number.

It is not a de Polignac number, because 21101657 - 2⁸ = 21101401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21101651) 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 3 ways as a sum of consecutive naturals, for example, 2969 + ... + 7142.

It is an arithmetic number, because the mean of its divisors is an integer number (5278464).

Almost surely, 2^21101657 is an apocalyptic number.

It is an amenable number.

21101657 is a deficient number, since it is larger than the sum of its proper divisors (12199).

21101657 is a wasteful number, since it uses less digits than its factorization.

21101657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12198.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21101657 is about 4593.6539921940. The cubic root of 21101657 is about 276.3368820994.

Adding to 21101657 its reverse (75610112), we get a palindrome (96711769).

The spelling of 21101657 in words is "twenty-one million, one hundred one thousand, six hundred fifty-seven".