21702057 has 16 divisors (see below), whose sum is σ = 31889088. Its totient is φ = 13043520.

The previous prime is 21702049. The next prime is 21702059. The reversal of 21702057 is 75020712.

It is not a de Polignac number, because 21702057 - 2³ = 21702049 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21702059) 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, 4794 + ... + 8147.

It is an arithmetic number, because the mean of its divisors is an integer number (1993068).

Almost surely, 2^21702057 is an apocalyptic number.

It is an amenable number.

21702057 is a deficient number, since it is larger than the sum of its proper divisors (10187031).

21702057 is a wasteful number, since it uses less digits than its factorization.

21702057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13000.

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 21702057 is about 4658.5466617820. The cubic root of 21702057 is about 278.9332582740.

Adding to 21702057 its reverse (75020712), we get a palindrome (96722769).

The spelling of 21702057 in words is "twenty-one million, seven hundred two thousand, fifty-seven".