21437378551 has 4 divisors (see below), whose sum is σ = 22369438512. Its totient is φ = 20505318592.

The previous prime is 21437378507. The next prime is 21437378561. The reversal of 21437378551 is 15587373412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21437378551 - 2³¹ = 19289894903 is a prime.

It is a super-2 number, since 2×21437378551² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21437378561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 466029946 + ... + 466029991.

It is an arithmetic number, because the mean of its divisors is an integer number (5592359628).

Almost surely, 2^21437378551 is an apocalyptic number.

21437378551 is a deficient number, since it is larger than the sum of its proper divisors (932059961).

21437378551 is an equidigital number, since it uses as much as digits as its factorization.

21437378551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 932059960.

The product of its digits is 705600, while the sum is 46.

The spelling of 21437378551 in words is "twenty-one billion, four hundred thirty-seven million, three hundred seventy-eight thousand, five hundred fifty-one".