21489877 has 2 divisors, whose sum is σ = 21489878. Its totient is φ = 21489876.

The previous prime is 21489833. The next prime is 21489883. The reversal of 21489877 is 77898412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12453841 + 9036036 = 3529^2 + 3006^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21489877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21489827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10744938 + 10744939.

It is an arithmetic number, because the mean of its divisors is an integer number (10744939).

Almost surely, 2^21489877 is an apocalyptic number.

It is an amenable number.

21489877 is a deficient number, since it is larger than the sum of its proper divisors (1).

21489877 is an equidigital number, since it uses as much as digits as its factorization.

21489877 is an evil number, because the sum of its binary digits is even.

The product of its digits is 225792, while the sum is 46.

The square root of 21489877 is about 4635.7175280640. The cubic root of 21489877 is about 278.0212403763.

It can be divided in two parts, 21489 and 877, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21489877 in words is "twenty-one million, four hundred eighty-nine thousand, eight hundred seventy-seven".