21372681 has 32 divisors (see below), whose sum is σ = 33592320. Its totient is φ = 11950400.

The previous prime is 21372679. The next prime is 21372697. The reversal of 21372681 is 18627312.

21372681 = T₂₇₈ + T₂₇₉ + ... + T₅₃₀.

It is not a de Polignac number, because 21372681 - 2¹ = 21372679 is a prime.

It is a super-2 number, since 2×21372681² = 913582986255522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21372641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 21526 + ... + 22496.

It is an arithmetic number, because the mean of its divisors is an integer number (1049760).

Almost surely, 2^21372681 is an apocalyptic number.

It is an amenable number.

21372681 is a deficient number, since it is larger than the sum of its proper divisors (12219639).

21372681 is a wasteful number, since it uses less digits than its factorization.

21372681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1037.

The product of its digits is 4032, while the sum is 30.

The square root of 21372681 is about 4623.0597011070. The cubic root of 21372681 is about 277.5149184415.

Adding to 21372681 its reverse (18627312), we get a palindrome (39999993).

The spelling of 21372681 in words is "twenty-one million, three hundred seventy-two thousand, six hundred eighty-one".