21407157 has 12 divisors (see below), whose sum is σ = 31429164. Its totient is φ = 14037120.

The previous prime is 21407153. The next prime is 21407159. The reversal of 21407157 is 75170412.

It can be written as a sum of positive squares in 2 ways, for example, as 2692881 + 18714276 = 1641^2 + 4326^2 .

It is not a de Polignac number, because 21407157 - 2² = 21407153 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21407157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407153) 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 11 ways as a sum of consecutive naturals, for example, 18948 + ... + 20045.

It is an arithmetic number, because the mean of its divisors is an integer number (2619097).

Almost surely, 2^21407157 is an apocalyptic number.

It is an amenable number.

21407157 is a deficient number, since it is larger than the sum of its proper divisors (10022007).

21407157 is a wasteful number, since it uses less digits than its factorization.

21407157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39060 (or 39057 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21407157 is about 4626.7868980536. The cubic root of 21407157 is about 277.6640568747.

Adding to 21407157 its reverse (75170412), we get a palindrome (96577569).

The spelling of 21407157 in words is "twenty-one million, four hundred seven thousand, one hundred fifty-seven".