21722157 has 6 divisors (see below), whose sum is σ = 31376462. Its totient is φ = 14481432.

The previous prime is 21722153. The next prime is 21722167. The reversal of 21722157 is 75122712.

It can be written as a sum of positive squares in only one way, i.e., 21706281 + 15876 = 4659^2 + 126^2 .

It is not a de Polignac number, because 21722157 - 2² = 21722153 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21722157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21722153) 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 5 ways as a sum of consecutive naturals, for example, 1206778 + ... + 1206795.

Almost surely, 2^21722157 is an apocalyptic number.

It is an amenable number.

21722157 is a deficient number, since it is larger than the sum of its proper divisors (9654305).

21722157 is a wasteful number, since it uses less digits than its factorization.

21722157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2413579 (or 2413576 counting only the distinct ones).

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

The square root of 21722157 is about 4660.7034876722. The cubic root of 21722157 is about 279.0193457892.

Adding to 21722157 its reverse (75122712), we get a palindrome (96844869).

The spelling of 21722157 in words is "twenty-one million, seven hundred twenty-two thousand, one hundred fifty-seven".