20951261 has 2 divisors, whose sum is σ = 20951262. Its totient is φ = 20951260.

The previous prime is 20951251. The next prime is 20951263. The reversal of 20951261 is 16215902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17222500 + 3728761 = 4150^2 + 1931^2 .

It is a cyclic number.

It is not a de Polignac number, because 20951261 - 2⁶ = 20951197 is a prime.

Together with 20951263, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20951261.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20951263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10475630 + 10475631.

It is an arithmetic number, because the mean of its divisors is an integer number (10475631).

Almost surely, 2^20951261 is an apocalyptic number.

It is an amenable number.

20951261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20951261 is an equidigital number, since it uses as much as digits as its factorization.

20951261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 20951261 is about 4577.2547449317. The cubic root of 20951261 is about 275.6788122916.

It can be divided in two parts, 20951 and 261, that added together give a palindrome (21212).

The spelling of 20951261 in words is "twenty million, nine hundred fifty-one thousand, two hundred sixty-one".