21929437 has 2 divisors, whose sum is σ = 21929438. Its totient is φ = 21929436.

The previous prime is 21929393. The next prime is 21929443. The reversal of 21929437 is 73492912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15319396 + 6610041 = 3914^2 + 2571^2 .

It is a cyclic number.

It is not a de Polignac number, because 21929437 - 2¹⁵ = 21896669 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21929396 and 21929405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21929447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10964718 + 10964719.

It is an arithmetic number, because the mean of its divisors is an integer number (10964719).

Almost surely, 2^21929437 is an apocalyptic number.

It is an amenable number.

21929437 is a deficient number, since it is larger than the sum of its proper divisors (1).

21929437 is an equidigital number, since it uses as much as digits as its factorization.

21929437 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 37.

The square root of 21929437 is about 4682.8876774913. The cubic root of 21929437 is about 279.9040359917.

It can be divided in two parts, 21929 and 437, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21929437 in words is "twenty-one million, nine hundred twenty-nine thousand, four hundred thirty-seven".