21426931 has 2 divisors, whose sum is σ = 21426932. Its totient is φ = 21426930.

The previous prime is 21426929. The next prime is 21426973. The reversal of 21426931 is 13962412.

21426931 = T₃₇₇₈ + T₃₇₇₉ + T₃₇₈₀.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21426931 - 2¹ = 21426929 is a prime.

It is a super-2 number, since 2×21426931² = 918226744157522, which contains 22 as substring.

Together with 21426929, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21426931.

It is not a weakly prime, because it can be changed into another prime (21426901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10713465 + 10713466.

It is an arithmetic number, because the mean of its divisors is an integer number (10713466).

Almost surely, 2^21426931 is an apocalyptic number.

21426931 is the 3780-th centered triangular number.

21426931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21426931 is an equidigital number, since it uses as much as digits as its factorization.

21426931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2592, while the sum is 28.

The square root of 21426931 is about 4628.9233089348. The cubic root of 21426931 is about 277.7495242315.

The spelling of 21426931 in words is "twenty-one million, four hundred twenty-six thousand, nine hundred thirty-one".