21157739 has 2 divisors, whose sum is σ = 21157740. Its totient is φ = 21157738.

The previous prime is 21157699. The next prime is 21157751. The reversal of 21157739 is 93775112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21157739 - 2⁸ = 21157483 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21157699 and 21157708.

It is not a weakly prime, because it can be changed into another prime (21157039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578869 + 10578870.

It is an arithmetic number, because the mean of its divisors is an integer number (10578870).

Almost surely, 2^21157739 is an apocalyptic number.

21157739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21157739 is an equidigital number, since it uses as much as digits as its factorization.

21157739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13230, while the sum is 35.

The square root of 21157739 is about 4599.7542325650. The cubic root of 21157739 is about 276.5814729384.

The spelling of 21157739 in words is "twenty-one million, one hundred fifty-seven thousand, seven hundred thirty-nine".