21942157 has 4 divisors (see below), whose sum is σ = 21957696. Its totient is φ = 21926620.

The previous prime is 21942143. The next prime is 21942191. The reversal of 21942157 is 75124912.

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 21942157 - 2⁷ = 21942029 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21942457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5413 + ... + 8554.

It is an arithmetic number, because the mean of its divisors is an integer number (5489424).

Almost surely, 2^21942157 is an apocalyptic number.

It is an amenable number.

21942157 is a deficient number, since it is larger than the sum of its proper divisors (15539).

21942157 is a wasteful number, since it uses less digits than its factorization.

21942157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15538.

The product of its digits is 5040, while the sum is 31.

The square root of 21942157 is about 4684.2456169590. The cubic root of 21942157 is about 279.9581442537.

The spelling of 21942157 in words is "twenty-one million, nine hundred forty-two thousand, one hundred fifty-seven".