20151971 has 4 divisors (see below), whose sum is σ = 23030832. Its totient is φ = 17273112.

The previous prime is 20151961. The next prime is 20151973. The reversal of 20151971 is 17915102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17915102 = 2 ⋅8957551.

It is a cyclic number.

It is not a de Polignac number, because 20151971 - 2¹⁴ = 20135587 is a prime.

It is a super-2 number, since 2×20151971² = 812203870369682, which contains 22 as substring.

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 20151971.

It is not an unprimeable number, because it can be changed into a prime (20151973) 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, 1439420 + ... + 1439433.

It is an arithmetic number, because the mean of its divisors is an integer number (5757708).

Almost surely, 2^20151971 is an apocalyptic number.

20151971 is a deficient number, since it is larger than the sum of its proper divisors (2878861).

20151971 is an equidigital number, since it uses as much as digits as its factorization.

20151971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2878860.

The product of its (nonzero) digits is 630, while the sum is 26.

The square root of 20151971 is about 4489.0946748760. The cubic root of 20151971 is about 272.1275488514.

The spelling of 20151971 in words is "twenty million, one hundred fifty-one thousand, nine hundred seventy-one".