21001969 has 2 divisors, whose sum is σ = 21001970. Its totient is φ = 21001968.

The previous prime is 21001961. The next prime is 21001979. The reversal of 21001969 is 96910012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16646400 + 4355569 = 4080^2 + 2087^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001969 - 2³ = 21001961 is a prime.

It is a super-2 number, since 2×21001969² = 882165403753922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21001961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500984 + 10500985.

It is an arithmetic number, because the mean of its divisors is an integer number (10500985).

Almost surely, 2^21001969 is an apocalyptic number.

It is an amenable number.

21001969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001969 is an equidigital number, since it uses as much as digits as its factorization.

21001969 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 21001969 is about 4582.7905254332. The cubic root of 21001969 is about 275.9010401015.

The spelling of 21001969 in words is "twenty-one million, one thousand, nine hundred sixty-nine".